Face masks effectively limit the probability of SARS-CoV-2 transmission | Hacker News Reader

Face masks effectively limit the probability of SARS-CoV-2 transmission

science.sciencemag.org

324 pointspaultgriffiths359 comments

This entire study seems to be centered around a theoretical, mathematical model, and I didn't see any attempt to actually validate that model.

Basically, the authors seem to assume that the virus behaves according to their formulas, and show that under their assumptions, face masks work, but don't actually prove that their assumptions match reality - or did I miss something?

No you didn't miss anything - most people upvoting this didn't read anything more than the title.

It invites rigor in studying mask efficacy. Some studies out there show inconclusive results of mask usage, and this article helps give us an explanation as to why we might be seeing that. The model shows that in an extremely virus-rich environment masking can be rendered ineffective, but in virus-poor environments, even surgical masks decrease the probability of infection.

Researchers need to measure concentration of virus in the environment as well as mask usage to show the efficacy of masks in real world situations.

Indeed this is the money paragraph:

"The effectiveness of masks, however, is still under debate. Compared to N95/FFP2 respirators which have very low particle penetration rates (around ~5%), surgical and similar masks exhibit higher and more variable penetration rates (around ~30-70%) (2, 3). Given the large number of particles emitted upon respiration and especially upon sneezing or coughing (4), the number of respiratory particles that may penetrate masks is substantial, which is one of the main reasons leading to doubts about their efficacy in preventing infections. Moreover, randomized clinical trials show inconsistent or inconclusive results, with some studies reporting only a marginal benefit or no effect of mask use (5, 6). Thus, surgical and similar masks are often considered to be ineffective. On the other hand, observational data show that regions or facilities with a higher percentage of the population wearing masks have better control of the coronavirus disease 2019 (COVID-19) (7–9). So how to explain these contrasting results and apparent inconsistencies?

Here, we develop a quantitative model of airborne virus exposure that can explain these contrasting results and provide a basis for quantifying the efficacy of face masks. "

So they are left with a conundrum that places which use surgical masks seem to be better off, whereas randomized control studies of surgical masks show little to no benefit. This is what they try to explain with a mathematical model.

The mistake that many people make, and that I think you're implicitly making here too, is this notion of "controlled study". If the study denies the result seen time and again in real life, perhaps the study isn't studying correctly.

How many agains makes the study wrong

If we fully understood what was happening in real life, we wouldn't need studies.

> On the other hand, "observational data show that regions or facilities with a higher percentage of the population wearing masks have better control of the coronavirus disease 2019 (COVID-19) (7–9)." So how to explain these contrasting results and apparent inconsistencies?

My hypothesis regarding surgical mask prevalence and how it correlates with better virus control:

People who wear masks--however effective they may be--also behave in other ways to limit the spread. They minimize time spent in public indoor spaces, they keep distance from other people, they're more likely to self-quarantine if a family member is sick, etc.

The mask-wearing prevalence is a proxy for how serious the wearer takes Covid as a threat.

It’s worth also considering the case of ski helmets. Since these have became common on the slopes head trauma has actually increased because wearers take more risks.

Probably related to the uptake in snow boarding.

I had previously read that WW1 saw an increase in head injuries when helmets were used, due to victims surviving previously fatal injuries. However on searching it doesn't seem that clear-cut.

I definitely noticed a change in behavior at stores and at weddings I photographed once the mask mandate happened. Before it happened? Small backyard ceremonies with just families. In stores people straight up avoided being close to others.

After? Normal, but with masks.

Yeah, or the idea that maybe helmets in gridiron football increase CTE.

I see the possibility, but my own anecdotal experience with mask wearers and non-wearers jives with the other correlation: that non-wearers generally didn’t take the pandemic seriously.

The people that I know who shunned masks also ignored the COVID threat in other ways: Large gatherings, vacations to another state to escape lockdown restrictions, etc.

Whereas my religiously-masked friends were basically isolated last year.

And because I have several such anecdotes, I now have data :)

I wore a mask indoors. Then I got the vaccine. COVID is effectively over, unless we need booster shots this fall.

But feel free to wear a mask as much as you want, at this point it is effectively a security blanket though.

Same here. The only time I'm wearing a mask now is when the establishment asks me to. Otherwise, I'm back to normal.

Pre-vaccination, I was an indoor-only wearer.

Or is it that people are taking the same amount of risks, but accidents that used to cause death are now "merely" causing head trauma?

(I don't know either way, just curious to know if this angle has been investigated.)

This is probably more likely. Risk compensation (people behaving more dangerously when they have more safeguards) basically doesn't happen - it's an excuse to not use the safeguards. When seatbelts were introduced lots of people were opposed because it encouraged driving, or because they wanted the chance to just roll out of the car if it was about to crash.

This is not clear cut: see this review which concludes that this is not the case (helmets neither increase injuries nor risky behaviour). In general the idea of risk compensation is frequently brought up in these cases, and while it may seem intuitive, it usually does not appear in the data.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3989528/

"Some people with swine flu travelled on a plane from New York to China, and many fellow passengers got infected. Some researchers looked at whether passengers who wore masks throughout the flight stayed healthier. The answer was very much yes. They were able to track down 9 people who got sick on the flight and 32 who didn’t. 0% of the sick passengers wore masks, compared to 47% of the healthy passengers. Another way to look at that is that 0% of mask-wearers got sick, but 35% of non-wearers did."

https://slatestarcodex.com/2020/03/23/face-masks-much-more-t...

At the beginning of the pandemic I was skeptical about the effectiveness of masks and this article is what convinced me that there is some benefit.

What is astounding to a lot of us in South East Asia is the reluctance of the West in learning from our lessons. How many deaths and personal trauma experiences do people in general need to go through in order to learn from others?

There is a strong culture of individuality, and that is coupled with an extreme reluctance to just do what we're told, and what I mean by that is more about trust than Authority. Trust is low here, which is problematic for a scenario like this.

Many of us did learn those lessons.

For me personally when this all began, checking out what the world is doing seemed the natural thing to do.

The US is also very insular, in that a smaller percentage of people travel abroad than is typical for many Western Nations. And a small percentage of people seek news produced outside the nation too.

Both of those stats are better elsewhere in the West, so make of that what you will.

I think it goes further than individuality, though. There's a pervasive selfishness that seems to run through our (American) culture. Many who do believe that COVID is a threat to others (say, to older people, or to immuno-compromised people) but do not believe that they themselves are in much danger will decide not to wear a mask because they don't think it matters to them if they do or not.

This is the thing that makes me saddest. It just seems like people in the US are unwilling to endure even a minor inconvenience if it will help someone else but not do anything for themselves.

It seems pretty selfish to force small businesses to close and not allow people to earn a living, for a disease that has a pretty high survival rate and is only really a problem for old or very unhealthy people. And it goes against all pandemic guidelines from before 2020, which was to shield the vulnerable and let everyone get on with life more or less.

I agree strongly!

The idea of some effort, cost, minor sacrifice or inconvenience for a common, public good is not strong here.

Couple that being basically as insular on a personal level as we generally are nationally, and we find more of us than we may expect are empathy challenged too.

In the US, it's more to do with the way the CDC's messaging throughout the pandemic than any rejection of the evidence concerning a mask's efficacy.

People refusing to wear masks rarely question whether or not it works, and more to do with a low estimation of the disease's threat, as well as contempt for both the technocrats who chose to mislead the public about masks early on, and leaders who they believe are overstepping their authority by mandating them.

Our leadership has been doing everything possible to burn through its perceived legitimacy, and this is the result. Childish, spiteful, somewhat understandable behavior.

As someone who worked the public for the entire pandemic, id say it was about 50-50 between people who thought covid wasnt a threat and people who thought masks werent effective

who _has_ or who _did_? I take one of these as “the pandemic is over” which seems far from the case, generally...

Wasn’t it more a result of tribalism? Even before the masks were really a topic it became quite important politically for the pandemic to be real or not, depending on which group you hoped benefitted politically or not. From the outside it looked like everything more or less flowed from that starting point, and then everyone picked their positions and favorite realities from there.

No. And I say that due to my experience here in Sweden, with the same message spread around about masks. I understand why the government did it in the beginning of the pandemic, to save PPE from shortages, to avoid people using masks and getting a false sense of security, etc.

Still, it created a lot of distrust when the message changed a few months ago, it wasn't a tribalist issue and I can completely understand how people ended up with this distrust. They are still wrong and I completely agree with this comment [1].

[1] https://news.ycombinator.com/item?id=27231688

Interesting, thanks for sharing. How do you get to a high correlation between mask usage and political party in that scenario, though? If the underlying factor is truly inconsistency from the CDC rather than tribalism then (I think) you wouldn’t expect that.

https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3664779

I think the CDC mis-messaging is one component of this. Another is that there is no long tradition of public medical mask-wearing in the West, unlike many parts of SE Asia. Public mask-wearing is new, exceptional, and somewhat alarming if you live in North America or Europe.

Yet another component is that trust in the press and other public institutions was at possibly an all-time low in America at the time the COVID pandemic became public knowledge, and shows no signs of pulling out of that nosedive.

If you wore a mask in public in the UK before COVID, you would have got some very strange looks. They might have thought you were a criminal trying to hide your face. It seems fairly normal now though.

It's worse than that, you'd probably had been harassed by the police, or just simply arrested.

Don't agree that that's the case at all if you wore a mask on a packed tube commute for example.

Bullshit, while rare, more than a few people wore them in train stations or airports.

It was illegal in France to cover your face. They had to change the law.

> to mislead the public about masks early on,

"Hey, some government people lied to us saying we don't need masks, hence why we won't use masks now"

Great logic there. But hey, cutting your nose to spite your face feels good, no?

> "Hey, some government people lied to us saying we don't need masks, hence why we won't use masks now"

> Great logic there. But hey, cutting your nose to spite your face is nice, no?

Stupid people are gonna stupid, but you can't lie to people and then expect them to then automatically trust you when you're telling the truth. Those people are objectively and factually wrong, but they are right to be distrustful. If the issue wasn't one of science that we could otherwise objectively evaluate, their position would be perfectly rational and reasonable.

How about the complete lack of correlation between mask mandates and infection rates? But yeah, i must be stupid for looking at those.

Friends were talking about that a year ago. Health authorities in the west were completely ignoring their counterparts in Asia early on. Dismissed the threat until the pandemic blew up in Northern Italy and New York.

A lot of people in HN were arguing that the 0.7% fatality rate reported by Chinese authorities in Feb/20 was because Chinese medical care is bad.

Casual racism is kinda pernicious.

If you watched reddit all the comments to all news from China (including doctors dying, doctors not dying, hospitals being built or filling up, doctors clapping on TikTok because they'd released their last patients) was complaining about it and calling it fake news from the CCP. They were happy about the same thing from the US though.

Do you remember the posts about people dropping dead in the streets, people skin turning black, or massive cement mixers "disinfecting" streets? There was plenty of fake news going around.

The people spraying disinfectant everywhere was a bit silly but also not any different from what we were doing. At the time people out here were keeping their mail outside for 3 days and sanitizing their groceries.

> What is astounding to a lot of us in South East Asia is the reluctance of the West in learning from our lessons.

Agreed. We should have relocated Britain and NYC to the equator long time ago.

That is not “very much yes”, that is “an anecdote suggests yes”.

The statistical illiteracy here is astounding from professional scientists.

”0% of ths sick passengers wore masks, compared to 47% of the healthy passengers. Another way to look at that is that 0% of the mask wearers got sick, but 35% of non-wearers did”

And another way to look at it is that 65% of non-wearers didn’t get sick. The group of sick people is also quite small, meaning that the error bars on the effect size are large.

Sloppy, sloppy thinking.

Error bars would be nice. They're MIA in large swathes of COVID related research. I've read a lot of COVID papers in the past year and this paper is typical of the field. Things you should expect to see when reading epidemiology literature:

1. Statistical uncertainty is normally ignored. They can and will tell politicians to adopt major policy changes on the back of a single dataset with 20 people in it. In the rare cases when they bother to include error bars at all they are usually so wide as to be useless. In many other fields researchers debate P-hacking and what threshold of certainty should count as a significant finding. Many people observe that the standard of P=0.05 in e.g. psychology is too high because it means 1 in 20 studies will result significant-but-untrue findings by chance alone. Compared to those debates epidemiology is in the stone age: any claim that can be read into any data is considered significant.

2. Rampant confusion between models and reality. The top rated comment on this thread observes that the paper doesn't seem to test its model predictions against reality yet makes factual claims about the world. No surprises there; public health papers do that all the time. No-one except out-of-field skeptics actually judge epidemiological models by their predictive power. Epidemiologists admit this problem exists, but public health has become so corrupt that they argue being able to correctly predict things is not a fair way to judge a public health model[1]. Obviously they insist governments should still implement whatever policies the models say are required. It's hard to get more unscientific than culturally rejecting the idea that science is about predicting the natural world, but multiple published papers in this field have argued exactly that. A common trick is "validating" a model against other models [2].

3. Inability to do maths. Setting up a model with reasonable assumptions is one thing but do they actually solve the equations correctly? The Ferguson model from Imperial College, which we're widely assured is one of the world's top teams of epidemiologists, was written in C and filled with race conditions/out of bounds reads that caused their model to totally change its predictions due to timing differences in thread scheduling, different CPUs/compilers etc. These differences were large, e.g. a difference of 80,000 deaths predicted by May for the UK [3]. Nobody in the academic hierarchy saw any problem with this and worse, some researchers argued that such errors didn't matter because they just ran it a bunch of times and averaged the results. This is confusing the act of predicting the behaviour of the world with the act of measuring it, see point (2).

4. Major logic errors. Assuming correlation implies causation is totally normal. Other fields use sophisticated approaches to try and control for confounding variables, epidemiology doesn't. Circular logic is a lot more common than normal, for some reason.

None of these problems stop papers being published by supposedly reputable institutions in supposedly reputable journals. After reading or scan-reading about 50 epidemiology papers, including some older papers from 10 years ago, I concluded that not a single thing from this field can be trusted. The problems aren't specific to COVID, they're cultural and have been around a long time. Life is too short to examine literally every paper making every claim but if you take a sample and nearly all of them contain basic errors or what is clearly actual fraud, then it seems fair to conclude the field has no real standards.

[1] "few models in healthcare could ever be validated for predictive use. This, however, does not disqualify such models from being used as aids to decision making ... Philips et al state that since a decision-analytic model is an aid to decision making at a particular point in time, there is no empirical test of predictive validity. From a similar premise, Sculpher et al argue that prediction is not an appropriate test of validity for such model" https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3001435/

[2] https://github.com/ptti/ptti/blob/master/README.md

[3] https://github.com/mrc-ide/covid-sim/issues/116 https://github.com/mrc-ide/covid-sim/issues/30 https://github.com/mrc-ide/covid-sim/commit/581ca0d8a12cddbd... https://github.com/mrc-ide/covid-sim/commit/3d4e9a4ee633764c...

It gets worse.

You should look at the the observational studies measuring vaccine effectiveness in Israel coming from Balicer and his group.

They report the effect of the vaccine on number of positive cases without even mentioning that the vaccinated individuals are not routinely tested by ministry of health policy, or that the main reason people get tested is to shorten the isolation period after contact with covid-19 cases, which vaccinated individuals are exempt from.

Doesn't seem it corrects by seat position

> The mask-wearing prevalence is a proxy for how serious the wearer takes Covid as a threat.

But that’s the issue. Science is about finding the truth, not to map itself to trigger some desired social behaviors.

I fully agree with you. I was just trying to resolve the apparent incongruity between the results in the controlled setting vs the observational results.

There’s a (social) scientific explanation for that as well.

"proxy for how serious the wearer takes Covid as a threat." I would suggest that this now law in some countries and that would be the reason for wearing facemasks.

There is also a question as to the extent to which the current rules send a signal to be careful or not. Anecdotally and highly subjectively, I felt like when schools were closed here in January, everybody started being more careful generally - as though closing schools went a strong message that it was time to be cautious again, more than just announcements about virus rates would have done.

I suspect that in locations with a higher prevalence of masking the population is generally more vigilant: more hand washing, more social distance, stay at home when ill, avoid obviously ill people, and so on. May be a case of correlation, not causation.

It would be interesting to have a trial where everyone was wearing N95s, but we're not likely to see that.

>It would be interesting to have a trial where everyone was wearing N95s, but we're not likely to see that.

Bavaria and Austria had FFP2/KN95 only while the rest of Germany had the choice of surgical masks or FFP2, where almost everybody picked surgical masks (cheaper, not as annoying to wear).

Now the rest of Germany switched to only FFP2 in public transport.

So we do have some population studies. It didn't seem to make much of a difference. I'd say the factor overwhelming almost every other measure is the weather. More people outside means dropping case numbers. More people at home means rising case numbers.

It's been true for influenza and cold, and it's still holding up for Corona.

If any measure would make sense it would be to allow people to meet outside while forbidding it at home. They only forbade at home without allowing outside meetups, which made home parties more likely.

Ventilation could also be a factor. You're more likely to open the window when the air outside is pleasant.

True, which is why it's even more important to get people to meet outside.

If you forbid inside and outside meetups, people will meet in secret, even closing their Windows so the neighbors don't snitch (this is Germany after all, the nation of snitches, historically :D).

A little bit of basic human psychology could have prevented some of these waves.

> I suspect that in locations with a higher prevalence of masking the population is generally more vigilant: more hand washing, more social distance, stay at home when ill, avoid obviously ill people, and so on. May be a case of correlation, not causation.

The states with the highest mask use (NYC, CA) has some of the highest covid positive rates, so the data does not seem to back up your assertion.

You seem to be repeating this in several comments, but that's just not true. CA's total per-capita case counts and recent new-case rate is lower than, say, both Texas and Florida.

NYC is not a state, so you can't directly compare it.

The confirmed cases to population is 10.3% for NY (not NYC- 2.08m cases to 19.4m population), 9.5% for CA (3.77m cases over 39.5m population), 10.1% for texas (2.93m cases over 29m population), 10.6% for Florida (2.29/21.48).

Deaths to confirmed cases is about 1.6% for all except NY. NY death to cases is 2.6% (52k deaths over 2m cases). However, this way of computing deaths is only indicative as you do not capture untested cases.

> Florida 2.3M cumulative cases & 3,007 case/day 7-day average vs 21.5M population.

That's about 10.6%.

> FL and TX are worse on per capita cumulative cases, and much worse on current per capita new cases than California.

With the total cases being about the same so this does not support your conclusion that masks "drastically reduce spread".

The RCTs I have seen with basic surgical masks also seem to focus only on protection of the wearer, whereas on a societal level wearing even a shitty mask may be helping to prevent spread by presymptomatic people. I think it is unlikely the positive outcomes in mask wearing communities are purely due to confounders, although of course they probably also play a role.

I suspect mask wearing increases social distancing. That would explain much of the data but satisfy neither political party.

I'm not sure about that honestly. At the extreme there's definitely COVID deniers who followed no precautions, but IME most "normal" people I know felt more comfortable spending time indoors with masks than they would have otherwise. And 6 feet is really not enough spacing in many indoor environments. With things like elevators the other person could be gone and you could still be exposing yourself.

There is also precedence for some of these statistics with Asian countries during the SARS pandemic, and in these places rule following is generally much better.

And with a smaller sample size there are some case studies from restaurant transmission. Staff seem to get infected less frequently than other diners, even though they are in the space for longer. There are a few possible explanations, but the fact that staff don't take their masks off is a pretty compelling one.

> Staff seem to get infected less frequently than other diners, even though they are in the space for longer. There are a few possible explanations, but the fact that staff don't take their masks off is a pretty compelling one.

IMO that’s the least compelling reason. One big one would be the staff having way more contacts and thus higher exposure to the other circulating hCoVs as well as SARS-2 itself.

The evidence for face masks is weak at best. In my opinion they don’t even make sense theoretically unless you pretend that droplet transmission is the dominant transmission mode, which is completely unproven yet widely believed dogma (go figure)

It is possible for there to be multiple modes of transmission, and there is good evidence to suggest droplet transmission plays a meaningful role in COVID spread. How much it contributes versus airborne transmission may be debatable, but that doesn't mean taking preventative measures against droplet transmission is "dogma". Here is some discussion of evidence for droplet transmission https://jamanetwork.com/journals/jama/fullarticle/2768396

I'm also not sure why you would assume staff have had more contacts. The people that were eating at indoor restaurants in the middle of the pandemic were unlikely the type to be limiting their contacts. Most case studies also checked for antibodies after the fact, not just active COVID testing, so prior immunity would have been detected.

What I don't understand... the UK was already doing challenge studies (intentionally infecting consenting volunteers).

Why didn't they make one with masks? Really can't be that hard to take a known infected person, sit them on a chair, arrange 100 people around them for a few hours with masks applied in a checkerboard pattern, and observe the results.

This is usually out of question for ethical reasons, but they already decided that that wasn't an obstacle, so why not (also) do a study on this?

(Or rather, arrange 10x 10 people, in 5 rounds putting a mask on the infected person.)

The challenge studies they’re doing involve infecting people with measure doses of the virus. An infected person may or may not be shedding at that particular moment. Once they’ve established the MED to infect someone, they could potentially do a study with aerosols and masks, but even then, trying to simulate the right airflow and volume of viral particles is probably too difficult to be practical.

tl;dr- There wasn't really a conundrum to explain related to mask-effectiveness at different levels. Rather, it's more like a lack of good data, as prior studies being cited were ridiculously weak.

---

This seems like a largely helpful characterization.

However:

> So they are left with a conundrum that places which use surgical masks seem to be better off, whereas randomized control studies of surgical masks show little to no benefit. This is what they try to explain with a mathematical model.

There wasn't really a conundrum. When the study writes:

> Moreover, randomized clinical trials show inconsistent or inconclusive results, with some studies reporting only a marginal benefit or no effect of mask use (5, 6).

, the two studies they cite with inconclusive data are ridiculously weak.

The first one (their "5") is [https://academic.oup.com/jid/article/201/4/491/861190]. This was published in 2010, with data from 2006-to-2007, for "influenza-like illness" (not SARS-CoV-2, nor even influenza (explained below)). Apparently they asked students living in the dorms to do certain behaviors for weeks at a time. They concluded:

> Conclusions: These findings suggest that face masks and hand hygiene may reduce respiratory illnesses in shared living settings and mitigate the impact of the influenza A(H1N1) pandemic.

And if that sounds inconclusive, yeah.. their study was ridiculously under-powered. In fact:

> This study has several limitations. First, influenza incidence was low, so it is likely that most ILI cases were not associated with influenza infection, even though the study was conducted during the influenza season.

So not only were they not writing about COVID, apparently the authors argue that most of the cases probably weren't even influenza. There're other huge problems with this study too.

The second one (their "6") is [https://pubmed.ncbi.nlm.nih.gov/33205991/]. This study assigned subjects a recommendation to wear masks -- presumably some who were recommended to wear masks didn't, while some who weren't recommended to wear masks did.

Even then, their statistical analysis was very noisy:

> Although the difference observed was not statistically significant, the 95% CIs are compatible with a 46% reduction to a 23% increase in infection.

And their stated limitations:

> Limitation: Inconclusive results, missing data, variable adherence, patient-reported findings on home tests, no blinding, and no assessment of whether masks could decrease disease transmission from mask wearers to others.

Point being that there's not really a conundrum related to things not fitting together so much as a simple lack of good data.

The problem is people are not lab mice, you can't purposefully expose a test group to a virus to get clean data. So you either have to work with noisy data (as the previous studies you criticize) or turn to modelling (as this study does). This doesn't negate their value in either case.

No need to be so picky.

In the absence of good data, the fallback is a position of ignorance -- not acceptance of bad data.

The prior studies were neither well-done nor directly relevant. As such, they didn't constitute good evidence on the topic of mask-wearing for the recent pandemic. The proper understanding would then be that the effectiveness of masks was little informed by such studies.

> The effectiveness of masks, however, is still under debate

Effective for the mask wearer, or effective for others in the vicinity of the mask wearer?

It's well established that cheap cloth masks and procedure masks don't protect the mask wearer very much.

The rationale for cheap masks is that they drastically reduce the spread of particles from the wearer to everyone else nearby.

If your goal is to protect yourself, wear an N95 or better.

If your goal is to protect a population, and N95s aren't available, then the cheap mask help a lot when people wear them.

Except there is no convincing evidence that they actually do help others, and the whole theoretical mechanism is centered around catching large respiratory droplets which is at odd with the totality of evidence pointing towards aerosol being the dominant mode. I would add if droplet transmission is the dominant mode, which I very much doubt, then masks would still fail in a real-world setting when you look at the fact they make conversational partners stand closer or speak louder, and the massive cross contamination that happens to almost everybody wearing these pieces of cloth over their faces (hands touch mask, mask touches hands, etc)

> no convincing evidence

This MIT study [0] was pretty convincing.

They conclude that "face masks can be an extremely effective indoor safety measure".

For example:

If an infected person was riding on a commercial airline with 100 other people, other passengers would be at risk of infection within 70 minutes. If all of the passengers wore masks, however, that space could be safe for up to 54 hours.

[0] https://www.pnas.org/content/118/17/e2018995118

How can a model be convincing if it hasn't been extensively tested in the real world?

The model of wearing masks has been extensively tested in Asia. Meanwhile US doctors were telling me that putting on a mask would actually cause you to get infected faster because you'd do it wrong. (Then the CDC announced mask orders the next day and they mumbled something about new evidence to me.)

And we can see who's done better in the last year.

It's looking more and more like a whole bunch of Asian countries just got lucky. Singapore, Taiwan and Vietnam have all currently got uncontrolled community spread again (possibly China too), and whilst the Taiwan outbreak could maybe be blamed on them getting sloppy Singapore has been aggressively enforcing mask wearing the whole time.

There was already good reason to suspect this was the case over a year ago too. The early outbreaks mostly seemed to be a gradient emanating outwards from Italy, with genetic testing suggesting that even the US had done reasonably well at halting spread from China and its big outbreaks came from Europe; Asia is obviously a long way from Italy and it was suspicious that a bunch of countries that in reality had widely varying policies on things like masks, testing, etc showed such similar results. Including countries like Australia and New Zealand that were more or less western in terms of culture but were geographically close to the rest.

Basically all convincing evidence for mask use is models (like the linked article) and in vitro unrealistic tests; whereas in real world data, the best I could find wrt covid is 2% reduction.

Bacteria are a different matter, and possibly other viruses. But real world data about covid is that masks make very little difference either way, and are possibly harmful.

People touch their faces all the time, mask or not. And some non-physical effects of masks may be useful. If nothing else, fumbling around with masks is repeated reminder for all other measures.

It may feel silly to wear a mask if you belief that this is the only effect. But you cannot deny that it is a causal effect, e.g. it would not happen without wearing the masks.

I wear "n95" masks while sanding drywall, obviously trying to make the fit as good as possible, and still my boogers end up with tons of plaster in them. I would assume these particles to be bigger than any virion.

A properly fit N95 should block out all dust. If you are getting plaster in your nose, try different types of masks (folding), or a half-face respirator.

One of the justification for not advising N95s to the public was the fact that most people don't know how to properly wear one. As if they couldn't be trained in a few weeks, or duration of the pandemic.

Also, N95s filter out particles smaller than .3 microns (the 95% part). You can look it up, but it has something to do with the electrostatic media and physics. It definitely does not work like a sieve. (https://www.usatoday.com/story/news/factcheck/2020/06/11/fac...)

Actually it DOES work like a sieve on larger particles. The electrostatic mechanism works on smaller particles, while the larger ones are indeed filtered "mechanically".

The 0.3 micron size is used in the specification because it's the "worst" case... too large for maximum electrostatic attraction, too small for mechanical filtration...it's the worst case.

You are here talking specifically of N95 masks, not cloth masks, and this is only true for the very few that properly use masks. Doctors are required to not touch N95 mask and dispose of them after each use. Viruses can live for up to 24hrs on a mask and spread from you touching the mask then another surface.

Covid survives for 30 seconds in sunlight, so wearing a mask outside is bad on balance as you breathe in your own CO2 and reduce oxygen intake which both have negative health effects (especially during exercise).

Unless you have a valve, and hardly breath at all, exhaling pushes the N95 away from your face enough to let some unfiltered air in. There’s a similar (though smaller) effect with the thin paper valves, but regardless of how good the fit is, you need a much better valve than that to actually filter all air through the fabric.

Are there N95's without a valve? Cause all I've owned before the pandemic had a valve.

Yes.

I’ve had both with and without valves since 2015. Would never buy one without a valve again if I can find one with a valve (in the last year at some times could only find valveless)

Fwiw, in Israel it was illegal to use a valved mask without covering the valve with cloth/paper/surgical mask. The official statement was that the pressure out of the valve disperses virions much farther, and is thus more dangerous to people around you if you are presymptomatic than having no mask at all.

When wearing a mask in a hospital setting I had to have a fitting done. A test was run and a machine measured particles getting through. Properly fitted, nothing got though down to a very small size (which I don't recall).

An earlier version of the test saw some particle released into the room and a properly fitted mask wouldn't let it though. If people could smell the chemical, the fit was poor.

And I assume you were also trained in how to use the masks properly so that they didn't increase chance of virus spread and only used N95 masks? E.g. don't touch mask and dispose/clean the mask after each use.

Almost nobody does this, and many use cloth masks.

> I would assume these particles to be bigger than any virion.

The masks aren't expected to stop individual virus particles. They are supposed to catch salivary droplets containing the virus.

These are probably bigger than particles of drywall dust.

Yep, what most people forget when talking about N95 and similar is how a "standardized" fit test is performed, basically the 95% is theory and only IF the mask is properly fitted.

You will have deep signs on your face after wearing a fitted N95 a feww hours.

Previous posts with some more details and link to a US Department of labour video: https://news.ycombinator.com/item?id=27129984 https://news.ycombinator.com/item?id=23957506

> then the cheap mask help a lot when people wear them.

Are there any reliable and conclusive studies supporting this?

There are not even any reliable studies showing that surgical masks help during surgery. The problem with public health agencies is that, apparently, if they don't have an RCT they immediately jump to make the worst possible decisions. So try not to do the same thing.

> There are not even any reliable studies showing that surgical masks help during surgery.

That's fine, because I am not a surgeon and I don't care.

I do care about fogging up my glasses and having to speak up without any proper evidence that wearing a mask helps significantly against covid.

The kind with a bendable bar or tape at the top for your nose don't affect my glasses.

Anyway, you're going to run into the same problem doctors' advice has, where everything not required is forbidden. If a 100-year problem like a pandemic comes up, try some unproven precautions, it's better than not doing anything until it's mandated.

> The rationale for cheap masks is that they drastically reduce the spread of particles from the wearer to everyone else nearby.

If so, why does states with the highest mask use (CA, NYC) have much higher covid rates than states with some of the lowest mask use (Florida, Texas)?

> If so, why does states with the highest mask use (CA, NYC) have much higher covid rates than states with some of the lowest mask use (Florida, Texas)?

They...don’t (leaving out NYC because the other three things are large, diverse states and NYC is a single large city):

California 3.7M cumulative cases & 1,336 case/day current 7-day average vs. 39.5M population

Florida 2.3M cumulative cases & 3,007 case/day 7-day average vs 21.5M population.

Texas 2.9M cumulative case & 2,034 case/day current 7-day average vs. 29M population.

FL and TX are worse on per capita cumulative cases, and much worse on current per capita new cases than California.

(case numbers from usafacts.org)

Also consider age distribution/population density in areas you compare.

Death rate is exponential in age, so small differences in age distribution gives big differences in relative deaths.

Death rate to confirmed cases is TX 1.7% (51k deaths over 2.9m cases), Florida 1.56% (36k deaths over 2296 cases), CA 1.64% (62k deaths over 3.74m cases) [source: google coronovirus stats]. So data does not confirm your conclusion.

Without stats on the age distribution of confirmed cases (even before considering the absence of analysis of confounding factors, liking case timing within the pandemic, etc.), I’m not sure how you can say the data doesn’t confirm the conclusion since you don’t have data on the proposed independent variable at all.

Yes, age distribution matters as older people are at higher risk. As some signal for this Florida is USAs old people home, so you would expect that if masks had a large positive mitigatory effect then Florida with its low mask use would do worse than CA and NY that has low mask use. However, we do not see this.

> As some signal for this Florida is USAs old people home, so you would expect that if masks had a large positive mitigatory effect then Florida with its low mask use would do worse than CA and NY that has low mask use.

Again, this has a problem of failing to address case timing and distribution, with CA and NY being hard hit and having COVID into the community before there was much awareness or any policy response (e.g., targeted control measures directed at elder facilities) or personal behavior response or evolution in treatment protocols, which radically changes the dynamic vs. states that weren't hit until after public awareness and health care competence was more advannced.

And presumbaly, you mean “CA and NY with high mask use”, otherwise this argument is nonsense. OTOH, no one has cited any data supporting the “CA and NY are representative of high mask use states while FL (and TX, as claimed in other posts) are representative of low mask use” argument, which seems to be based on stereotyping based on dominant political parties in each state and leanings of political leaders of each party on mask mandates. What data there is on this doesn’t seem to support that this stereotyping accurately reflects mask use, OTOH; i.e., a study on mask use with self-reported data for May through August of last year had mask use as:

AUG: CA 74.6% > FL 71.6% > NY 69.6% > TX 69.1%

JUL: NY 80.6% > CA 74.3% > FL 66.9% > TX 66%

JUN: NY 56.4% > CA 48.7% > FL 45.1% > TX 42.4%

MAY: NY 46.1% > CA 45.2% > TX 43.8% > FL 43.5%

APR: CA 38.1% > NY 36.1% > FL 35.0% > TX 32.4%

And, notably, all four states were in the top half of the country in mask use in all 5 months with data.

https://journals.plos.org/plosone/article?id=10.1371/journal...

I tend to trust state policy and political leanings more as an indicator then a self reported study. Can you please dig into why you trust this self reported study on the politically charged mask use question? Especially when the study is performed by academics that is perceived to be too often left-wing activists by republicans and many libertarians? (And according to Haidt have a provably largely left leaning bias)

Self reported results are prone to preference falsification and hidden bias in whom answers. (“Yes, mom, I did my homework” ;) )

Self reported results of politically charged questions are effectively polls. To indicate the problem you can observed how inaccurate polls around politically charged choices has become when compared to actual choices.

The normal problems with self reported results are probably aggravated by how academics, major authorities, media, and tech companies have openly without cover used force to promote the “right” answer and suppressed the “wrong”. The use of force to enforce specific conclusions had been an extraordinary and very noticeable break from western traditions.

> I tend to trust state policy and political leanings more as an indicator then a self reported study.

I don’t, in the absence of strong enforcement of policy (which did not exist in, e g., California COVID policy), especially on issues of strong partisan posturing; even solid red or blue states tend to be pretty closely balanced in the population; majoritarianism, reinforced by gerrymandering and related mechanisms, produces strong and durable political dominance from slight population imbalances, so “state dominant party” stereotypes and state policy vastly exaggerate differences in distribution of individual belief, preference, and, in the absence of effective compulsion, behavior.

> To indicate the problem you can observed how inaccurate polls around politically charged choices has become when compared to actual choices.

They...haven’t, really, become particularly inaccurate. Poll-based predictions of binary outcomes of things that poll very close to even have become somewhat less reliable than they very briefly were before (they were a fairly new practice compared to just reporting polls without predictions, anyway, so its not like there was a well-established baseline) because when polls are near even, very slight changes in accuracy have an outsize effect on binary predictions.

NY (not NYC) cumulative cases is 2m and population is 19.4m, so about 10.3% of population [source: google coronavius stats].

> California 3.7M cumulative cases & 1,336 case/day current 7-day average vs. 39.5M population

Its 3.77M, so about 9.5% of population.

> Texas 2.9M cumulative case & 2,034 case/day current 7-day average vs. 29M population.

That's 10%.

> Florida 2.3M cumulative cases & 3,007 case/day 7-day average vs 21.5M population.

That's about 10.6%.

> FL and TX are worse on per capita cumulative cases, and much worse on current per capita new cases than California.

With the total cases being about the same so this does not support your conclusion that masks "drastically reduce spread".

> With the total cases being about the same so this does not support your conclusion

I didn’t offer any conclusion except that the upthread claim that California had a much higher rate of COVID cases than FL/TX was bunk. To actually tease out the effects of mask use from jurisdictional case statistics, you’d also have to (1) have stats on mask use, which (despite people making claims about it in coordination with blatantly false claims about cases), I haven’t seen, and (2) have good stats for the other things that would reasonably be expected to contribute to differences in infection spread, (3) either have enough a priori knowledge of the contribution of the items in 2 to control for their effect in 1:1 comparisons, or have data from enough different places to do an analysis that determines the contributions of different factors.

Even with good mask stats, a head to head comparison of a couple states case numbers with mask stats wouldn’t otherwise be useful for anything.

>To actually tease out the effects of mask use from jurisdictional case statistics, you’d also have to (1) have stats on mask use, which (despite people making claims about it in coordination with blatantly false claims about cases), I haven’t seen, and (2) have good stats for the other things that would reasonably be expected to contribute to differences in infection spread, (3) either have enough a priori knowledge of the contribution of the items in 2 to control for their effect in 1:1 comparisons, or have data from enough different places to do an analysis that determines the contributions of different factors.

Absolutely, 100% with you. And effectiveness of a mitigation should be determined before mandating it, and the positives and negatives of the mitigation should be well understood.

> I didn’t offer any conclusion except that the upthread claim that California had a much higher rate of COVID cases than FL/TX was bunk.

I was responding to the parents claim that masks “ drastically reduce the spread” which I think I’ve showed is an unsupported claim, although I stated my initial claim too strongly. There is no significant observable effect on state covid case count or state death to confirmed case count (which would to some degree control for some differences in testing).

> Even with good mask stats, a head to head comparison of a couple states case numbers with mask stats wouldn’t otherwise be useful for anything.

After one year of mandating this mitigation we should be able to see some observable difference to continue mandating that people cover their faces. This is not zero-cost, especially for the ones living alone, as the masks block facial expressions showing emotion and the masks make it harder to breathe which can on aggregate cause health issues. For instance, a large number of dental issues is caused by mask use [1].

[1] https://fineartsdentistry.com/how-face-masks-are-affecting-o...

I really don’t get why this is still considered a conundrum

Lots of places have R hovering around 1. If it goes to 1.1 everything goes to shit, if it drops to 0.9. Everything will be fine.

So even if masks reduce spread by a tiny amount, even 10% better. That could easily swing you below 1 and save the day.

10% would not be tiny, that would be a statistically huge percentage based on population counts.

The CDC study concluded 2% reduction. That’s in the range where harms need to be weighed too (e.g. masks that aren’t replaced often enough harbor bacteria themselves; there’s environmental costs, etc)

The trouble is that this doesn't actually work. By using R this way you're assuming a model where every person is equally likely to spread the infection to every other person in the population, which is easy to calculate but what actually happens. In reality people can only spread the virus to those they're in contact with, and (say) a supermarket employee can spread the virus to more people than someone working from home and not socializing due to social distancing rules. Not only that, there are clusters of people who are all likely to spread the virus to more people or to less people when infected, such as workers in food manufacturing, people in dense urban areas vs less dense areas, etc...

So what actually happens in reality is that if R is hovering around 1, there are going to be some places where it's actually above 1 and cases are growing exponentially, and some where it's below 1 and they're shrinking exponentially. The end result of this is that places where R is actually below 1 make up an exponentially shrinking proportion of all cases, and as this happens it causes the overall measurement of R to go back above 1.

Ok, makes sense. But why does this make any difference to the crux of my argument? - if that supermarket employee is wearing a mask, they’re going to spread it to less people.

R=1.1=everything goes to shit is not a valid inference. R is just the derivative of the case graph. It can and does change on a daily basis, says nothing about absolute levels, and says nothing about how it will evolve over time or what the actual peak levels of infections will be. You can find "exponential growth" in nearly any graph if you want, look at a sine wave for example, and viruses in particular are a curious choice to describe this way because epidemics show S-curve logistic growth, not exponential. It's very confusing to people that it's so often described as exponential because that implies unbounded and very rapid doubling until a day/serial interval before saturation half the population is infected at once, whereas we know that epidemics don't do that in reality.

Ok so what I mean is r being 1.1... over time.

I think you’re looking to find holes in a perfectly reasonable argument by adding complexity.

Over how much time and how does that variable relate to the actual length of time an epidemic of an (apparently) seasonal respiratory virus is expected to last?

I don't think it's just a nitpicky minor thing. Governments have pretty regularly been making decisions and citing the value of "R" (they mean Rt), or "exponential growth", as a justification for new restrictions, apparently without realizing that by itself these things means little and justify nothing. Exponential growth can only be said to be a problem when taking into account the serial interval, the actual exponent, the starting population sizes, total population sizes, fixed capacity limits (e.g. hospital bed counts) and so on. Yet the scientists advising governments routinely ignore all those things.

> observational data show that regions or facilities with a higher percentage of the population wearing masks have better control of the coronavirus disease

Which is also not entirely true. There are quite a lot of regions (data from worldometer, statista) that have a better control of the virus despite people not giving a crap about face masks. For instance, Florida has 1600 deaths/M vs 3000 deaths/M in New Jersey. What'd be the explanation?

https://www.worldometers.info/coronavirus/usa/new-jersey/

https://www.worldometers.info/coronavirus/usa/florida/

It looks like New Jersey was hit early on (when it was also rampant in New York) and Florida got hit later. It could be that hospitals do better at treating it now. Obviously that's speculative. But there are like 30 things I could think of that would make it difficult to make direct comparisons between states. Climate is another one -- Florida is nice all year round, so you can have family/friend gatherings outdoors. I also live in a warm state, and we've just done family/friend stuff outside, even Christmas. At this point we do things indoors when everyone there is vaccinated, and outdoors otherwise. In the case of Florida, turns out all those people that ignored restrictions and went to the beach were something like like 20x less likely to spread it than people spending time indoors. Again... speculative. Point being, you'd have to somehow have the data you need to properly control for a multitude of factors if you wanted to make direct comparisons (including some solid reasoning on what to control for).

I don't understand this myth about Florida. It has fared very badly in the pandemic. You're three times as likely to have died in Florida from COVID, as opposed to in Canada. It sits in the middle of the States, in terms of death rates, which overall have been among the worst in the world. Compare your example to an area where people really take masking serious, such as Hong Kong, and then maybe you'll have a valid comparison.

It's not a myth. I'm looking at statistics right now. A myth is that Florida has fared very badly (most likely a politically inspired myth). Compared to other states, it hasn't. It's indeed in the middle, meaning that Florida does better than half the states of the USA. It's on par with California numbers, but I've never heard anyone (in the media) slamming very badly on Cali.

I honestly don't believe that a mask can make such a MASSIVE difference when it comes to Hong Kong vs USA numbers. I don't have the answer, but it's something else, something foundationally different that makes them less prone to catching the virus. Genetics? No idea. I mean, c'mon, I can smell literally everything around me when I'm wearing a mask, but it protects from a virus? I'm not an expert by any means, but something tells me it's a joke.

> I don't have the answer, but it's something else, something foundationally different that makes them less prone to catching the virus.

Compare China to the US on: https://en.wikipedia.org/wiki/List_of_countries_by_obesity_r... . Obesity is the second biggest contributor to covid severity after age.

I think you missed my point that the United States has fared very badly and that Florida sits right in the middle of the pack, in the States. California has fared very badly as well, but that's a separate point. I think many Americans are so insular, they forget there's more to the world than just the States.

US hasn't fared that badly, they are in the middle, as far as per population goes. But that isn't really the point, it maybe it is. The point is that comparing California and Florida, they did roughly the same, despite attacking the issue differently. This isn't to say how well Florida or California did compared to the rest of the world.

>Compare your example to an area where people really take masking serious, such as Hong Kong, and then maybe you'll have a valid comparison.

It's not fair to compare the US/Canada with East Asian countries like Hong Kong because the biggest contributor to covid fatality rates apart from population age is obesity rates, which are way lower in East Asia.

I haven't clue about statics so it's likely this is wrong but a quick graph of COVID deaths per million vs obesity rate for each country doesn't look like there is any correlation.

https://jsgist.org/?src=7b456a001284587cb90c7693ac0e6f3b

Also, if age is the #1 factor then Japan should have the worst covid as they have the most old people per capita but they don't. They also haven't locked down but they have worn masks. (not saying masks were why covid is so low here). Yes they are having a spike now. It's still tiny (1/20th) other countries with comparable populations sizes.

Japan is kind-of locked down, mostly by canceling large events and keeping people home. They're working on the principle that covid has mainly aerosol transmission and is spread by rare superspreaders rather than just everyone.

It's working okay but not as well as Korea.

Japan isn't keeping people home. Restaurants are open (till 8pm). People are commuting in crowded trains, etc... I walk by the restaurants and cafes and they're plenty busy.

Did everyone give up on remote work?

Or Washington state for an example in the US. They take masks very seriously and are one of the lowest in the countries in terms of effected.

I live in Hong Kong. The mask mandate here is entirely pointless, and has not made any difference to our handling of the pandemic.

What has on the other hand is extremely aggressive tracing, tracking, and quarantining of all potential contacts. I've had a few friends who were unlucky enough to get caught up in a cluster, and the ones who caught it got out of the hospital far quicker than their contacts got out of their government quarantine. Rather aggressive tactics, but it's effective.

But it's obvious that masks had nothing to do with it. There are plenty of unmasked activities (dining, drinking etc) that haven't spawned clusters, while masked activities (gym, dance club) spawned our big clusters.

I think it's hilarious that everyone who commented on this completely ignored your given examples of Florida and New Jersey, and instead chose to compare Florida to completely different places, that just-so happen to make Florida look bad.

Regardless of strategy, every country in the northern hemisphere that had a decent number of cases in spring 2020, got absolutely hammered in winter 2020.

Of course there are examples of regions where the one with more restrictions got a better result than the one with less. But there are simply way too many counter-examples where regions that did more, tried more, had more restrictions, still got a similar or worse outcome than comparable regions that didn't.

Here's a pretty fun quiz that highlights this complete lack of correlations in the actual data: https://www.covidchartsquiz.com/

Considering that the vast majority of cases of COVID are asymptomatic, it’s pretty apparent that the viral load needed to infect someone enough that they even exhibit symptoms, never mind need to be hospitalized, is not easy to achieve. As such, it’s likely even a 30% reduction (which is on the lower end of the range) in the viral load inhaled by someone could drastically reduce the chance of symptomatic COVID.

And when you combine 30% reductions for both the receiver and the emitter, it gets much higher.

That's not how infections work though. A high initial load can cause the infection to peak higher (because more replication occurs before the immune response), but a lower initial load doesn't necessarily lead to a low peak infection (because replication is exponential with a large exponent).

That doesn't make a lot of sense. Higher initial load means higher severity but a lower initial load doesn't mean lower severity?

A lower initial load doesn't guarantee a low severity because the timing of the immune response is such a big factor (due to the large reproduction exponent).

As such, it’s likely even a 30% reduction (which is on the lower end of the range) in the viral load inhaled by someone could drastically reduce the chance of symptomatic COVID. is vague enough to not be an over statement, but it probably isn't easy to find much in the way of actual support for it either.

A lower initial load leading to less severe disease makes intuitive sense (less opportunity for the infection to outpace the immune response) and whilst not proved, a lot of virology experts think it's plausible.

There is at least some evidence for it, e.g. a military base study that found less severe disease cases once masks started being worn.

Ah yes the "randomized controlled" studies 5 and 6.

5 is about influenza and 6 is not even worth the paper it's printed on.

No kidding, 6 is "recommending" people to wear a mask (and not even trying to control for the actual number).

So no, I have no qualms in calling study 6 useless, I've seen science fair projects with more scientific rigor and relevance than that.

Working down from the conclusion to find the necessary assumptions is the standard approach to COVID-related questions.

This is a valid way to do science.

"What assumptions are required to make this conclusion valid?"

If the assumptions turn out to be outlandish, then maybe we can't take the conclusion to be true.

In principle, sure, but here, it's just grotesque.

They admit RCTs show masks don't matter, so they put together a few differential equations (which most certainly could be chosen differently to support something else entirely) such that in some domains (virus-limited) masks help a lot, in some (virus-rich) not.

Then they implicitly assume that RCTs didn't show anything because they were done in virus-rich environments and somehow conclude from this dubious claim that "Face masks effectively limit the probability of SARS-CoV-2 transmission".

Am I not reading it correctly?

Probably not. Most things like this are like this. There may indeed be some underlying proof, but they either can't or won't show it to you-if it exists. It is more likely that it does not. They start with their conclusion. They rarely commence an empirical study, because that might prove their prepared conclusion wrong! A model, which can be used in place of reality, is not reality, and never will be. GIGO. The model was tailored to match their wanted results, or more likely they made a bad model and tweaked it to gain desired results. This does not mean that masks are bad-it just means that the methods used are generally false. Properly gained empirical evidence should be used, and it even should not be trusted if it points to you doing something stupid-like wearing a tissue on your face all day.

The paper is fine, the title is clickbait.

Nope. It's circular. We need actual tests in the wild, not models.

During an interview with some of the doctors sent into Wuhan in their wave, they claimed none of the 10 thousand or so doctors sent in became infected. They used strict PPE protocol, including N95 masks.

Given what we know about the covid transmission now, it was absolutely the N95s that prevented these doctors from getting infected.

Alternatively it could also be flawed data on infections, which we know is already highly likely.

Then run a proper randomized controlled trial with comparisons to cloth and surgical masks so we have actual data, not 10000 anecdotes.

This was the biggest event of the last 50 years, we can throw a few billion at a real trial.

One problem--ethics.

Can't knowingly give humans less protection. It's not a money problem.

That is what you are testing!

Equipoise demands you don't assume one outcome.

Otherwise every single pharmaceutical trial would be impossible since "we can't knowingly give humans a placebo"

If the effect is large and significant we will see it quickly and can halt asap.

>Otherwise every single pharmaceutical trial would be impossible since "we can't knowingly give humans a placebo"

Lots pharma trials are against current best standard of care and not placebo. Placebo trials are never done in cases where effective therapy is available.

https://www.cancer.net/research-and-advocacy/clinical-trials...

>A: Placebo-controlled trials are never appropriate when a highly effective or potentially curative therapy is available for a patient. An exception is unless the trial allows the patient to receive the new treatment/placebo in addition to the potentially curative therapy. For example, let’s say that a promising new treatment is in development for advanced testicular cancer, a disease that is curable in many cases with the use of chemotherapy. It would not be appropriate for a clinical trial to randomize patients between the new treatment and placebo because potentially curative chemotherapy already exists. However, it might be appropriate to randomize between standard chemotherapy plus the new drug or standard chemotherapy plus placebo because in both cases, patients will receive the standard, potentially curative treatment.

"29. The benefits, risks, burdens and effectiveness of a new method should be tested against those of the best current prophylactic, diagnostic, and therapeutic methods. This does not exclude the use of placebo, or no treatment, in studies where no proven prophylactic, diagnostic or therapeutic method exists."

https://en.wikipedia.org/wiki/Placebo-controlled_study#Decla...

If I remember rightly, what they actually claimed is that none of the doctors sent in were infected in the hospitals. That is, there were doctors sent to Wuhan who caught Covid, but the Chinese government blamed it on them becoming infected from contact with people outside of their work.

My thinking has always been that of all the possible interventions to reduce viral spread, something like making people wear masks while grocery shopping has almost no negative side effects. Whereas closing the grocery store altogether has major negative side effects, like lost jobs and people not being able to buy groceries.

So I think the evidential bar for requiring masks should be pretty low (unless it is a special case, like making people wear masks when they're exercising likely has larger negative side effects). Who cares if it may not do much? The cost of doing it is so low.

Whereas the evidential bar for policies that do more collateral damage ought to be higher.

If masks turn out to be ineffective, the cost of having them recommended is reduced reputation and authority.

Would you take security advice from Bruce Schneier after he proposed you to cover your keyboard in snakeoil because it might protect against computer viruses (and if not, there is not much damage)?

That's an absurd comparison.

Regardless of how well they work in practice, there's a clear theoretical reason why masks could/should work: they catch salivary droplets containing the virus.

Covering your keyboard in oil is not even theoretically going to affect your computer's susceptibility to computer viruses.

That’s the difference between theory and practice.

In practice the snakeoil may prevent you from using your computer more frequently and therefore result in less infections.

In practice I observe a lot of people fumbling out unwashed pieces of cloth from their pockets and placing them in their face, hoping it would preserve their respiratory health.

You are correct, although I wouldn't call this a study. It's a science paper, yes, but it doesn't contain any new data that has been studied, just some fancy formulas and graphs and conjecture by a couple of people with a science degree.

This has been the case with all of the non-pharmaceutical measures imposed. The models say they work, but real world data doesn't show much correlation.

N95/FFP2 seem to be very effective.

I wish the media and government would have spent more time in educating people in things like how N95 masks work and that it isn't like a coffee filter. Even thought the pores are larger than a virus the masks are statically charged causes smaller things to get trapped. Many people don't know this but probably had an interaction with static electricity sometime in school and would understand it if someone explained it. Instead people get put in a bucket and no dialog is possible.

Education is key to understanding. You can't reach everyone most.

I’m not sure there was any popular doubt over the efficacy of N95 masks. The problem was rather getting one - marketplaces like Amazon restricted access to masks if you weren’t affiliated with a hospital. So you were left with sketchy deals and weird vendor sites.

I suspect Amazon killed quite a few people over the last year by restricting access - supply scaled pretty quickly.

Unfortunately, a few of my friends fell victim to the Qanon conspiracy bandwagon and the fact that mask pore size is wider than the virus was heavily circulated as a reason for mask ineffectiveness.

That wasn't a Quanon conspiracy: that was misunderstanding that I saw plenty of mainstream doctors and other health professionals promote. What it showed is that either they were intentionally lying - which I kinda doubt - or that they were so confident in what they had heard that they never bothered to do any research for themselves. Just reading the relevant wikipedia pages carefully would have corrected that misunderstanding.

This is your not frequent enough reminder that "doctor" is not a synonym for "scientist", or more specifically epidemiologist.

Medical doctor's are basically mechanic's for the human body. The human body is complex, so this is a high bar to clear and an important function, but it doesn't magically grant them knowledge about concepts outside that field.

Everyone is having assumptions about these observations. The conclusions might not be always right, but at least the observation is real. And when you observe that mask mandating states don’t do significantly better than mask-free states, then a curious mind rightfully starts pondering. No need to unterstand conspiracy theories (a difficult topic) to understand that science isn’t getting it right yet.

> And when you observe that mask mandating states don’t do significantly better than mask-free states, then a curious mind rightfully starts pondering.

If this is true, which I haven't confirmed, wouldn't that say more about the effectiveness of political policy rather than about masks themselves? When we have seen throughout the pandemic that healthcare workers have a dramatically lower rate of infection compared to the general population, despite having more direct contact with infected populations, it is clear to the that proper precautions including protective equipment (principally masks, for a respiratory disease) can impede COVID transmission heavily. With that being the case, the question becomes: has mask policy been effective in getting enough people to wear masks properly and consistently, in states where it is mandated?

Q is a symbol used by pedophiles to say that they are pedos ;). Just look at "Q", and you will see what I mean. Nothing complex about it.

You could get halfway with other solutions. The 3-layer design with the synthetic layer in the middle tries to achieve the same idea. It's not going to be as effective as a certified N95, but it's better than a simple cloth. Not sure how common the idea was globally, but it was quite common to make them in Australia.

Unfortunately there is _absolutely_ popular doubt about this, and every other thing you likely think is obvious about covid and the world. I don't think educating people about masks is really the answer though. I don't know what the answer is, or if there even is one. Feel like our society is coming apart at the seams.

The US seems to have relied heavily on cloth masks, even long after the shortages were over. From my understanding, surgical masks are much more effective (while often being more comfortable) than community/cloth masks. (I don't have a source for this on hand, but the German government did ban cloth masks/require at least surgical masks in many areas for this reason.)

I suspect a lot of that was out of a desire to not appear as backtracking on a previous position.

According to the data presented, surgical masks are still highly effective even after converting the scales to linear. Add social distancing on top, it is almost as good as N95.

And I very much doubt that N95 masks are effectively utilized by the general public considering how many poorly fitted masks I have seen over the past year.

Before the pandemic there had been several studies looking at the efficacy of N95 vs. surgical masks at preventing the transmission of influenza in hospitals. Most of them never got anywhere because it was soon realized that even doctors and nurses cannot be trusted to wear and change masks properly during the daily routine. Let's hope things have improved by now.

> And I very much doubt that N95 masks are effectively utilized by the general public considering how many poorly fitted masks I have seen over the past year.

I agree. When people can't even wear surgical masks properly, there's no hope with an N95.

> Most of them never got anywhere because it was soon realized that even doctors and nurses cannot be trusted to wear and change masks properly during the daily routine. Let's hope things have improved by now.

At the very least, everybody is washing their hands. Before Covid, you couldn't even get all the doctors to do something even that simple.

This was an education issue. There were KN95 and KF94 masks available for purchase. I bought KN95 masks off Amazon sold by Amazon proper and later switched to KF94 when they became widely available. Both masks have similar performance to N95. Someone of the KF94 masks i bought showed 99% filtering effectiveness in government testing.

The problem is wearing mask is annoying and uncomfortable. If I have to choose, I'll choose the increased risk of covid all the time rather than wearing mask.

A big part of why they are annoying and uncomfortable is the lack of one-way valves to make it easier to breath in them. In industry, when you actually need to wear a mask/respirator, they almost always have valves.

Unfortunately, we got stuck on the "wear masks to protect others" narrative, and people who actually were at risk were prevented from wearing much more effective, much more comfortable, masks that would actually work well at protecting them. Eg here in Canada, it's illegal to wear a mask/respirator with a valve on a plane.

Not only that, there is one more thing to carry when you go out and impairment of social interaction because of lack of facial expression.

I don't think it is an unfortunate narrative. two people wearing masks without valves is twice the reduction in likelihood that either one gives the other covid. If someone does have covid the mask without the valve will greatly reduce the concentration of virus particles in the air around them. I think that is working as intended!

Masks that aren't worn correctly tend to have very low efficiencies, because the air just bypasses the mask at the edges. Depends on many factors like the type, how hard you are breathing, etc. But filtering just 20% of the air breathed in is quite possible. And let's face it, people intentionally wear them incorrectly all the time because they suck to wear.

If you and I both have 50% filtration, that's the equivalent of 75% filtration. For the person who is vulnerable, that is much less effective than just wearing a 95% minimum filtration valved N95 mask/respirator properly.

It's just ridiculous that an elderly man on a flight, sitting next to a healthy 15 year old more likely to be killed by a flu infection(1), will be told to take off his valved N95 respirator here in Canada, to protect that 15 year old. I have friends who have seen this happen first hand.

1) https://www.cdc.gov/flu/symptoms/flu-vs-covid19.htm

With the typical masks available to and worn by ordinary people, exhalation pressure seems to cause a lot of air to bypass the mask too - except that instead of doing it via a well-designed valve that redirects the airflow somewhere sensible, it blows out the top and steams up glasses or out the sides and towards whoever's standing behind you.

> Unfortunately, we got stuck on the "wear masks to protect others" narrative

Why is that "unfortunate"? Surely discomfort is less important than actually protecting life?

I'm my state we have a choice now and I still wear one most places except the gym. That's where my comfort vs risk threshold crosses. On that note one thing that's odd that I've observed in mixed mask rooms is that I don't like exposing my face to people who aren't exposing theirs. It's like my smile, a sign of peace, can't be reciprocated so I'm making myself vulnerable at their expense. I'll don a mask in mixed mask rooms not because of conformity per se, but what feels like defensiveness. My simian brain is thinking "you don't know if these are friendlies." I'm looking forward to any future psychological studies that explain this phenomenon.

I don't think people need to know how they work. They just need to know that those are what doctors wear and that they are very, very effective. And much better than a mask you make from ad hoc materials.

Once N95 masks became readily available and cheap, it was (and is) mysterious why people weren't being told to wear them to protect themselves instead of wearing whatever was at hand to sort of protect themselves and others.

If you tell me how something works and it fits within my mental model of the world then I will trust you. I will add this information to my mental model of the world.

If you tell me something works but can't explain how I will consider if the claim is worth evaluating then attempt to understand it myself before accepting it.

If you tell me to trust you with no explanation I will immediately distrust you.

That's reasonable and also what I would like. But what is the mental model of someone wearing their mask alone in the woods or in their car?

So, yes, we should explain why an N95 is better than a handkerchief, but it seems like there are plenty of people who don't care about the details and just need to be told that one is more effective.

The mental model of many wearing masks "alone" is that it's more annoying to take the mask on and off all the time than it is to just leave it on. Also, touching the mask constantly leads to concerns about contaminating your hands and then spreading that.

When Semmelweiss invented handwashing, all the other doctors ignored him because they didn't like his model, even though he had empirical evidence.

Similarly, people like to argue against things like the minimum wage because it doesn't fit some economic model, but they don't realize those models are made up post-hoc to fit older real world data that turned out to be biased and incomplete.

Oh, and the West had to deal with scurvy for hundreds of years after discovering the cure (lemon juice) because we'd invented the food poisoning and germ theories of diseases and so we refused to believe you could cure one with food.

So don't worry too much about modeling things.

Last I checked in Canada, N95 masks are still about 3$ a pop for disposable, single use masks from industrial distributors. Pre pandemic, we bought 3M 8210s for about 15 cents in boxes of 160. I wouldn't call the current situation available and cheap.

Oh, and if you thought surgical masks were mildly uncomfortable, N95s are an order of magnitude worst. They pretty much need a perfect seal with your face and the 3Ms use a really tight rubber band to achieve that. 2 bands, actually.

I currently work on site and wear surgical masks all day, it's fine. Not sure I would want to do the same if it was N95s.

The discomfort is a sign that they may work.

Not proof--but a sign.

They are expensive, and I do not reccommend wearing them. I do not reccommend doing anything, expecially anything that has a high chance of bringing unknown costs.

3M 8210s are US $26 for 20 now. $1.30 per mask seems pretty reasonable to me, but I've never bought them in industrial quantities so don't have that anchor.

I've worn N95s for hours (actually P95s which have a nicer seal) and I agree that they're less comfortable than less effective alternatives. But it is a bit curious that people are concerned enough to be wearing their homemade mask alone in a car or walking outside by themselves but are unwilling to endure the slight additional discomfort of a known effective mask.

> a known effective mask.

...if you got a real one, and not one of the less effective fakes.

I wear mine alone in the car or on the sidewalk frequently.

Not because I'm "afraid" but because I'm too lazy to take it on and off between every stop I'm going to make.

This attitude that people are wearing masks alone because they're afraid and/or stupid is toxic.

Not to mention fervently touching mask surface that could be contamination might not be a good idea, especially if there is a chance you might then touch your eyes.

Grant me the steel man. What's the mental model of the people wearing them outside on a walk in the woods or on a beach? Not the inconvenience of taking them off between stops at the bank and the drug store.

I don't know, but who cares. Maybe for pollen and dust allergies.

Part of the problem is everyone feels the need to judge others. Why does it bother you that people wear masks on the beach? Why can't you just let them be?

I don't care what the others are doing per se. In fact, I think it's optimal if everyone else would wear a mask all the time.

What bothers me is that the sort of inconsistency I described is emblematic of the same muddled thinking that the CDC has demonstrated throughout. This is a problem for a number of reasons.

When people don't understand the reasoning behind a policy they are less likely to comply with it and it will lead to excess deaths.

Another reason is that, if no explanation or an incoherent explanation is given for a recommendation, people have to decide whether to follow it based solely on trust or the authority of the recommender. I don't think either of these is good for the long term health of society. You can see how this problem has manifested itself in the resistance of many people to being vaccinated or wearing masks.

> Once N95 masks became readily available and cheap, it was (and is) mysterious why people weren't being told to wear them

Because they're difficult to wear. There are a bunch of photos on social media of HCPs who've got bruised faces after correctly wearing N95 / FPP3 for a day or two.

Tens of thousands of doctors manage to wear them every day without injury. So color me skeptical in finding social media testimony less than persuasive that a real issue exists with the proper use of masks.

The only time "N95" was uttered was last year, when we were being told: 1. Masks aren't needed; 2. Don't buy masks, healthcare workers need them.

It's unfortunate that we didn't go back to talking about proper masks before people started knitting them and making them out of rags and beads. One wonders what difference it might have made.

Bless your soul, but what I've learned from the way we handled the pandemic worldwide (and are still handling it) is that information that's readily available and should in theory reach everyone, flows ridiculously slowly, even among specialists and political figures, it's easily corrupted and distorted, and a loud ignorant minority counts as much in the public discourse, as the voices of millions of reasonable people.

I'd say we have more evolving to do. Both biologically and socially. Individually (some) of us are relatively smart. Together we're as dumb as a piece of wood.

Yeah, it's disappointing to see how I still see people wearing their masks incorrectly, e.g. just over the mouth and not covering their noses.

Sometimes I think human beings are advanced, but then I walk into a public toilet and I see evidence how many are still no better than animals. It's a simple technology, urinate into the hole where the water can wash it away and we'll remain hygienic, but a lot of people still fail at that.

There are a couple of defensible reasons that people don’t put their mask over their nose outdoors. Firstly, if you wear glasses, then on humid days your glasses can fog up to a degree that you can’t even cross the street safely.

Secondly, in some countries the public has chafed against laws requiring outdoor mask wearing in places that are not even remotely crowded. (In my own country, the same scientists advising the government on the COVID response have also opposed this law and urged the government to overturn it, arguing that it is clearly unscientific and only undermines the government’s credibility in getting the population to observe the public-health measures that really matter.) At that point, wearing a mask in a half-ass way is a way for the population to signal their discontent. It has happened that such laws were lifted when ruling parties saw mass flaunting of them, because such strictness might cost them the next election.

To elaborate, I saw these people inside a supermarket, where it's probably in their own interest to wear it properly. And no they weren't glasses wearers.

But yes governments just repeating unscientific rules also annoy me, I agree in the empty outdoors masks are most probably unnecessary. (This statement is hedged because hey, I'm not an epidemiologist). They emphasize the "6ft apart" stuff but not the ventilation of indoor places...

And they say outdoor dining is okay, so restaurants put up tents which are poorly ventilated, and hey, the fucking things are outside, that follows the rules, so that means they're safe, right?

I should just join Wonko the Sane outside the asylum...

This is just something that happens with masks. I think you're reading too much into it.

In years past in Japan, where mask-wearing was always common, I noticed that just covering the mouth and not the nose was quite common. It still covers most of what people are trying to cover (odor, droplets). Which would still help for the worst contributors to covid too. If people are feeling claustrophobic or legitimately having difficulty breathing, I think it's an acceptable compromise.

Also, if people are talking a lot, then the mask tends to get pulled down off the nose constantly due to jaw movement. Hence in Japan you'd see store clerks and people in such roles often wearing the mask that way. Also this happens practically every word for many kinds of cloth masks. So if you see a public speaker somewhere with a fancy cloth mask not covering their nose (a shaming target I've noticed on twitter etc.) they probably can't help it.

I can't help but look at some peoples' rejection of public health guidance in the US as "not a bug/won't fix."

The relevant authorities (including traditional mainstream media) injected politics into the public discourse, which destroyed trust in what should be a normal public health process. Not only that but the relevant leaders of agencies decided to try manage the supply of masks through "steering" the public by downplaying the usefulness of masks.

Distrust of untrustworthy leaders is a feature, not a bug.

Absolutely. Considering how long it took CDC and WHO to even acknowledge airborne transmission, even though the Chinese were very clear about it from very early on.

https://www.nytimes.com/2021/05/07/opinion/coronavirus-airbo...

"even though the Chinese were very clear about it from very early on" I'm not sure this adds as much credibility as you seem to think. See (for example) - propaganda videos of people dropping dead in the street in Wuhan in early 2020.

Not sure what you're getting at. Preprint for this paper was out in Apr 2020:

https://pubmed.ncbi.nlm.nih.gov/32240078/

Chinese health authorities not being a credible source of information throughout the pandemic?

I'm not defending what they did, but let's make the facts clear.

Initially (december?) they denied there was human-human transmission, and tried to down play magnitude of the virus.

And once Wuhan was locked down, they down played how harsh it was, cut out the media (with the excuse of not causing panic).

But even before Wuhan locked down, they allowed the release of the virus sequence (Jan 2020), their mitigation efforts in Wuhan (the field hospitals built there, the thousands of doctors sent there, the treatment strategy the doctors used, what worked, what didn't), the air borne transmission, treatment methods, and all of that.

I was following this pretty closely, and the Chinese released very relevant information very early on.

But when Italy got hit, it was like they didn't even bother listening to anything the Chinese already put out. The Italians re-discovered pronation, low oxygen flow intubation, anti blood clot medication, etc.

Blaming the Chinese health authorities for not being credible is fine. But simply discounting everything they said is stupid. And completely ignoring their information even with mounting other evidence because "The Chinese are not credible", is doubly stupid.

It's like the world put on stupid blinders, and just wished that the Chinese were lying and Covid would just disappear magically.

I don't suggest ignoring everything the Chinese health authorities said, that would be ridiculous. "Take everything China allows to be released to the West with a pinch of salt" is a sensible starting point though - you can use it as an input, but you have to be more skeptical of information fed to you by a communist-controlled authority than you would otherwise be, and you certainly don't add credibility by pointing out "the Chinese authorities said so".

My point is that even the "untrustable Chinese" were saying airborne transmission at the outset. And other evidence that they were right came pouring in from other countries like Korea, Hong Kong, Italy, etc right from the start.

The CDC and WHO's decision to deny airborne transmission 14 months into the pandemic is purely idiotic.

So who do I trust now? Independent Scientists. Basically Twitter, ffs.

True, but there was many other reasons to think masks would work. Its demonstrated efficacy in other coronaviruses and the cultural evolution of dense Asian countries to use masks as a way to combat virus transmission. The WHO and CDC behaved liked total idiots, setting the burden of proof way too high for what should've been a pragmatic, common sense decision made with some uncertainty. Not atypical of bureaucrats to miss such a layup.

I don’t think they were total idiots, at least not from the angle you’re pointing out. The CDC knew masks were effective, but they wanted to make sure masks were reserved for healthcare workers. Remember at the time nurses were given a single mask to use for multiple days, and many hospitals had drives to collect donated masks. The CDC lied to prevent the general public from making the situation worse. Was it worth the long-term loss of credibility? It’s easy to say no, but we’ll never know the counterfactual. For all we know some other issue would have become as politicized as masks were.

To me, this was a glaring reminder that public health deals with more than cold hard science. It’s about ensuring public health first and foremost, given the realities on the ground. See harm reduction as another example. Again, I’m not sure they made the right call here. But it wasn’t due to ignorance.

It's hard to attribute the same charity to the WHO. They were dragged kicking and screaming to mask recommendation and this happened many, many months into the pandemic, well after any concerns of mask shortages were alleviated.

I see your point about the CDC. But they should've recommended home made masks. Other countries did that. They messed up big time. It's impossible to know the counterfactual with perfect confidence, but we can make a sound judgement given what we know.

Why on Earth are you calling them “propaganda” videos, when China was trying to downplay the pandemic at the time?

See, this is one big reason we’re collectively dumb. Everyone and their big conspiracy theories.

There hasn't been a single case reported in the West, of anyone dying instantly in the street of COVID-19. Ergo, videos filmed within China, allowed by the authorities to be viewed outside China, purporting to show this scenario, are the very definition of propaganda.

We also saw videos of sick people left to die in Chinese hospitals from their own phone recordings. Is that also propaganda?

And no, a video of something that isn’t what we thought it is, is not the definition of propaganda. Propaganda has a goal.

This video doesn’t match a single goal China has. If it does name it.

Please don't take HN threads further into flamewar. You escalated more than once in this thread. We're trying to go the opposite direction here!

https://news.ycombinator.com/newsguidelines.html

I get where you are coming from but something I've learned from this pandemic is that "wear a mask" is too complex and burdensome for a significant proportion of people in the west...

We immediately face this issue: You should not act on information, or even knowledge. You should act on WISDOM. Wisdom is hard to gain, and yet it proves itself time after time to be better than the other forms of truth. Education is not the key; That would be wisdom. I do admit that most of what they teach is falsehood, and it would be better if it were truth.It would be better of there were no education at all than what we have now. In fact, it would be better to have no education system at all than to have a good education system that is liable to deteriorate. This is especially true when that system is a cost and a burden to and on society. Your information, however, is hardly better than the "n95 is coffee filter". There is no good proof on how airborne viruses are transmitted! Wearing a mask may do nothing, or it may do everything(Well, it can't do everything. Masks haven't stopped gov't from the vaccine)! It is likely that much of the transmission is not even caused by the oral and nasal areas, but instead is due to fecal aerosols. Our best solution may be the abolition of apartments and shared housing. SOme sort of filter should be put on the toilets, not on our faces. Cleansing chemicals(like bleach) should be put in the toilets, not in our arms.

Let us remember that choices should be made carefully, with consideration, and only once all of the facts are present.

Let us not be hasty-We must wait until a length of time has past in which effects which take alonger time to present themselves are presented.

This may require the foregoing of many necessary things. But such is the cost of life. Such is necessary to avoid death, or things much worse.

This comment is a pretty good argument for education reform, but likely not in the way you meant.

You rock dude ignore these haters king

> Even thought the pores are larger than a virus the masks are statically charged causes smaller things to get trapped.

Even filters that aren't statically charged stop particles that are smaller than the gabs between the fibers. There are actually several mechanisms by which a filter can stop a particle.

1. Big particles don't fit between the fibers of the filter. Think fish in a fish net. This is called sieving.

2. Particles too small for sieving but heavier than the surrounding flow don't make the turns as well as the surrounding flow when the flow goes around the fibers. The particles can get embedded in the fibers. This mechanism is called inertial impaction.

3. The smallest might be too small to actually be affected much by the flow of the surrounding fluid through the filter. The move by diffusion, and many will randomly hit the fibers and get stuck.

4. Particles too big for diffusion but too light for inertial impaction still can run into fibers and get stuck. This is called interception.

5. As you mentioned, some filters have an electrostatic charge which can help trap particles.

The effectiveness of sieving, inertial impaction, and interception all follow S shaped curves that start out low for small particles, then at some point start rising, and then level out. The sieving curve's rise is almost vertical. The rise for inertial impaction is steep but not nearly as steep as it is for sieving. The curve for interception's rise is much more relaxed.

The effectiveness for diffusion goes the other way. Much more effective for very small particles, then above some size drops down and is low from then one.

When you put all these together, you get a curve that is effective at the small end, and at some point as size goes up effectiveness drops, reaching a minimum, and then rises again to reach high effectiveness for particles above some certain size.

The reason 0.3 microns is used for many HEPA filter ratings is that is in the middle of the low part of that U shaped curve, so when you get a filter that removes, say, 99.97% of 3 micro particles, it should actually do better for both larger and smaller particles.

Here's a document that has some diagrams explaining all this, and has some graphs of the efficiency curves for mechanisms #1-4. http://donaldsonaerospace-defense.com/library/files/document...

You are being very generous in assuming the people in charge want you to be educated. It seems to me they wanted you to run around with a (relatively) useless cloth mask so they could horde the most effective masks for themselves.

> N95/FFP2 seem to be very effective.

Why does then the states with the highest mask use (CA, NYC) have much higher covid positive rates than states with some of the lowest mask use (Florida, NYC)?

> Education is key to understanding. You can't reach everyone most.

N95 masks improperly used will hold covid for 24hrs and spread them by the incessant touching most people do of their masks before they touch other things.

Education only works if the means as deployed are likely to have a positive effect, such as surgeons in a strict hospital settings (where they are still used the wrong way as most people still touch the mask).

> Why does then the states with the highest mask use (CA, NYC) have much higher covid positive rates than states with some of the lowest mask use (Florida, NYC)?

They don't. Stop spreading misinformation. (Also I love that in this repeat of your misinformation, you accidentally typed "NYC" where you meant to say "Texas". And it would behoove you to learn the difference between a city and a state.)

So to be accurate the confirmed covid cases to the population is about the same in states with and without mask mandated as well as other strict social distancing measures.

> Why does then the states with the highest mask use (CA, NYC) have much higher covid positive rates than states with some of the lowest mask use (Florida, NYC)?

Even if that was true, places that were hit hardest by the pandemic tended to impose the most severe restrictions.

It's like finding that crash barriers are installed on roads with the highest accident rate and asking whether crash barriers are useless.

People have traveled and moved extensively to Florida as well as TX from NY and CA, so any high-spread virus would spread to Florida and CA then spread within them.

If masks and other strict lockdown measures were effective then by now open states such as Florida and NYC would see much higher death as well as covid case rates. See other comment I made in parent thread showing its about the same.

Strict lockdowns are effective. It's a virus that spreads through social contact. You restrict social contact, you reduce spread of the virus. It's not plausible to claim they're not effective.

This feels like an argument from 12 months ago. They've demonstrably worked in Italy, the UK, New Zealand, China, and so on. They were the primary tool to constrain virus spread until vaccines came along.

What metric shows strict lockdowns are effective?

As I've shown outcomes on covid cases are equivalent in populous strict lockdown states (NY, CA) and open states (Florida, Texas). Death rate to confirmed covid cases is about 1.6% for all of these except NY that has 2.6%, controlling somewhat for differences in testing.

"This is an open-access article distributed under the terms of the Creative Commons Attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited."

So happy to see that.

Not that this will settle anything.

Anecdotally, I've not gotten even a slight cold while being socially distanced while consistently masked.

Well, that may be due to other people social distancing enough to keep the level of colds down. It might have nothing to do with masks.

anecdotally, I have very little social contact normally anyway, I've worked from home since before winter, and always wear masks in closed public spaces - have had 3-4 colds in that time.

I do have kids though.

My frequency of colds has increased 10x since I've gotten married and had kids.

Anecdotally, since taking vitamin D3 supplements I haven't been getting colds. Added daily nutritional zinc supplements in 2020 as soon as they were available after I heard the anecdotal evidence D & zinc are effective in Covid prevention. Throughout winter and early spring last year you couldn't get zinc supplements for love or money.

A lot of anecdotes there :).

The American medical establishment has a long history of not getting behind nutritional disease prevention. Some of it is for good reason, but I think there is also a systemic bias.

My 2yo would like to sneeze on you and flip that anecdote on its head.

Parent of a 1.5 year old here. Can confirm - several colds.

To the parent comment's point though, I haven’t had any colds in the last year where my daughter wasn’t sick first

They seem to have perpetual runny noses when they’re really young.

Years ago my entire family got sick and I was determined not to contract it through distancing and frequent hand washing and sanitizing. It worked until I bent down to tie my toddler’s shoes only to look up and mid-sentence have him cough directly into my open mouth. All it takes is one mistake. Needless to say I got sick shortly after.

I wonder what the result would have been if you immediately gargled with vodka.

I've used that successfully in the past to chase colds out of the throat before they get into my nose and lungs.

I’ll try that next time!

A few years ago I went on vacation for a week with a half-dozen friends in an Airbnb and spent the entire time miserably sick with some kind of respiratory illness. I was similarly determined not to get anyone else sick (and I was sick from the start, so avoided any asymptomatic period). I was fastidious about distancing and sanitizing, and any time I needed to cough I'd step outside of the house. Nobody else got sick. Is the sample size here large enough to determine anything? No idea, but I like the anecdote.

I'm not sure which explanation you are seeking to flip, but a sneeze can be cause by an adenovirus, which were apparently not suppressed this year as the influenza viruses and other four endemic coronaviruses were.

It's more plausible, at least in my view, that this is the result of suppression of several endemic respiratory pathogens by viral interference (something that has been observed in previous pandemics).

https://medium.com/illumination-curated/the-unexpected-case-...

It's not just an anecdote, it's measurable on a global scale [0]

[0] https://www.nature.com/articles/d41586-020-03519-3

Anecdotally I haven't had a cold in years. I work out 4 days a week and while I wouldn't call it a strict diet I have an upper limit calorie "budget" that I never exceed. While it's certainly possible that masks helped some people avoid all airborne transmissions last year, lots of people were also able to exercise more and make better food choices without the rush of breakfast and lunch commutes.

Get kids. They are plague carriers.

My dad used to refer to day care as "your friendly local disease exchange," because he and my mom would get sick whenever they visited grandchildren.

And a former colleague, then childless, called them "petrie dishes."

I made absolutely no changes 1 year, but because my workspace at work was in an alcove next to an air conditioning vent that pulled air from the outside, I completely dodged the office cold because I basically had my own positive pressure environment.

It's more likely your lifestyle is simply keeping you away from people and places that experience high levels of foot traffic.

I also wonder if some people just don't have as strong as immune response and so they get barely a sniffle from a typical cold virus.

>got a cold

That's because the cold virus is spread by surfaces, and you likely touched something with it, then scratched your eyes. You can be 80 miles from someone, but if you touch something he touched, you're potentially getting his cold.

> That's because the cold virus is spread by surfaces

Stop. There is no one virus called "the cold virus", and several of the viruses that do cause colds (including, for example, the other four endemic coronaviruses) are not known to spread by fomites.

You stop. Looks like we're both wrong: https://www.cdc.gov/features/rhinoviruses/index.html

It's either surface contact or ghosts coughing in the poster's face.

I didn't say that there aren't other viruses that cause colds that can be spread by fomites. I said that:

1) There isn't a single virus called "the cold virus"

2) In addition to SARS-CoV-2, there are other viruses that cause cold-like symptoms that are not spread by fomites.

Your comment gave the impression that there's a single "cold virus" for which fomite transmission is the primary vector. That's not so. There are a bunch of viruses (in fact a bunch of families of viruses) bunch that cause cold symptoms, and only a few of them are commonly spread by fomites. None of the five endemic coronaviruses are known to be among these, nor is influenza.

Also, even though the CDC appears to be correct to my eyes in this case, I urge that, after the disastrous departure from anything resembling science in the past year and a half, we stop regarding it as a credible source.

Stop again. Then read the link I posted.

I have read the link you posted many times. I am familiar (albeit at an arm's length, as an amateur) with rhinovirus, adenoviruses, coronaviruses, RSV, etc.

At the end of the day, you made a misrepresentation that, taken at face value, gives a false impression that might lead to bad conclusion with respect to control of these viruses.

There are dozens (some scientists believe hundreds) of viruses that cause cold symptoms. Fomite transmission has been reported in a few, though there is scant evidence at this point. In the vast majority, it has not. In some, like the endemic coronaviruses, it has been examined extensively and not found.

It's certainly worth further study!

But your assertion that suppression of fomite transmission - rather than viral interference - is the explainer of splitrocket not having contracted a cold is not well-founded, but might lead to them (or others) believe that this is a positive side effect of surface sanitization.

Now, has norovirus perhaps been suppressed by all the surface sanitization? Maybe. But not colds. The cold viruses appear to have been suppressed by viral interference (with the curious exception of the adenoviruses).

Attempts to suppress fomite transmission come at a significant cost, namely, increased antimicrobial resistance. It's important not to use this method of suppression in places where it will have no effect, such as attempts at population-level control of viruses that cause cold symptoms.

It has been a pleasant year in that regard. We finally went on a domestic trip to Atlanta a couple weeks ago, after having been fully vaccinated in the middle of April. Guess what we came back with? A cold. Dammit!

Objectively, it doesn’t seem to matter if an area is masked or not. The virus won’t be stopped. Just compare Florida to California or Georgia to Washington state.

I know what the models say. But my eyes deceive me.

Anecdotally, I spent an entire week, unmasked, in an apartment with someone sick with symptomatic Covid, and never caught it.

Anecdotes are not data.

I don't know. We had some of the highest mask wearing percentages in the country here in Southern California, yet some of the highest infection rates in the world. Something isn't adding up here. I'm guessing if everyone had N95 masks, we would have seen lower numbers however. I don't think the average cloth masks that people are wearing are very effective.

Could it have to do with population density (perhaps even only in certain areas)? My reasoning is that you could have high transmission among the minority that doesn't wear masks, and that might suffice to make the absolute case-load quite high.

Counterpoint: Miami

Miami-Dade County, FL has a little under half the cumulative confirmed cases as Los Angeles County, CA (500K vs. 1.2M) with a little over a quarter the population (2.7M vs. 10M), for a much higher per capita rate. So...how is it a counterpoint?

(Case numbers from usafacts.org.)

I don’t know the details here, but in the Israel vs Sweden comparison, absolute numbers favor Israel (7000 vs 14000 dead) but age normalized are the same (Sweden has about twice as many >60), and in European normalized excess death measures from Oxford, Sweden is at 2% and Israel at 6%

Personally, I try to only use excess death figures, because case counts are not comparable due to local policies. E.g. once vaccination started, Israel categorically stopped testing vaccinees unless they show clear covid symptoms; whereas it demands weekly test from many unvaccinated even though they have no symptoms.

> Personally, I try to only use excess death figures, because case counts are not comparable due to local policies.

Deaths are great measure of how bad you’ve been hit overall, but even if they (when you use excess rather than COVID-attributed deaths) are arguably more reliable numbers, they are a much worse proxy when you are trying to compare effectiveness specifically of infection control measures..That’s because they are extremely sensitive to when a region was hit during the pandemic (because we learned a lot about treatment over time), geographic distribution and time concentration of infections compared to local healthcare infrastructure (was treatment capacity exceeded anywhere, and by how much for how long?), as well as the population age distribution that you can try to adjust for by age normalization.

It is far from perfect; and yet, it's the only metric comparable between different countries, assuming you can trust death counts -- which I do for most countries. It's not a good proxy, but there is no better one that I've found (nor that I'm aware anyone else has found).

Every other measure has all of the problems you listed, and in addition it is subject to testing policy differences (including who to test, cycle threshold, and other variables), diagnostic policy differences (e.g., in the UK, death within 28 days of a positive PCR test is classified as death from corona, regardless of what happened since; Death more than 24 hours from a vaccine is assumed unrelated to the vaccine), and explicit number fudging.

> it’s the only metric comparable between different countries

There are a near infinite array of othere measures besides exceess deaths that are both comparable between countries and not, even approximately, measuring the thing being discussed, which is COVID infections, like GDP per capita PPP.

Not sure what you are trying to say here. Let's try again.

Are you aware of any other metric for covid infection, comparable between different countries?

Please pay attention to the examples I already gave about how numbers from Israel and the UK make, specifically, "cases" and "deaths from covid" non-comparable.

And remember that I do not dispute that "excess death" is far from perfect. My claim is that -- inherently -- every other measure of covid infection suffers from the same problems that "excess death" does, and then some.

In NYC the less dense areas had worse infections.

The problem in California might be crowding, ie it's not designed for the population density and so everyone has roommates or lives with an extended family. That would cause more indoor transmission, and I believe a lot of cases in CA were among working class people and Latinos.

Could it be that Southern California believes in masks too much? As in, they weren’t as cautious in other ways?

I wonder how much super spreaders affect outbreaks.

Let’s say LA had 50 super spreaders vs. 25 in SF. I’d expect LA to have more than 2x the cases because of the exponential spread of the virus.

And I think the idea behind masks was not that they’re a cure, but a 2nd best option if the best option of social distancing isn’t possible.

And even if they’re 30% effective, the idea is to get R (the number of subsequent people an infected person goes on to infect) to go down. Because a 30% reduction in transmission has a huge effect over time, even if it’s not perfect.

super spreaders and super spreader events are key to transmission, like indoor singing hallelujah or indoor family gatherings happy birthday granny or schooling, Kindergarden, you get the gist...

indoor and speaking/singing is the key combination for aerosol based transmission.

Zeynep Tufecki described this phenomenon in the Atlantic, going into its overdispersed nature of spreading and how most infections don’t result in a spread to others, but some circumstances become super-spreading events with an outsize impact:

https://www.theatlantic.com/health/archive/2020/09/k-overloo...

how do you measure mask wearing percentages? Socal seemed to have a lot of unmasked private gatherings throughout the pandemic. The draconian lockdown measures just pushed the spread underground.

So one can make a model out of thin air and not validate it, and then write a paper about it claiming to have the holy grail? That's Science in 2021?

>So one can make a model out of thin air and not validate it, and then write a paper about it claiming to have the holy grail?

That's Academic Finance in Forever.

Works best if it fits the bias/agenda of the journal editors. The better you do that, the more weaknesses they will forgive.

Here's the manufacturer's (3M) label:

WARNING: This respirator helps protect against certain particulate contaminants but does not eliminate exposure to or the risk of contracting any disease or infection. Misuse may result in sickness or death. For proper use, see supervisor, or User Instructions.

https://multimedia.3m.com/mws/media/1837275O/3m-9132-healthc...

Because they are just NIOSHA certified and not FDA. Only certain N95s are have gone through testing and certification to be cleared for medical use.

That's standard legal ass-covering.

Notice the word 'eliminate'.

Nobody could claim something would 'eliminate exposure or risk of contracting any disease' and not get sued immediately by someone who got sick.

In Wuhan, something like 10,000 doctors were sent in to treat the thousands in field hospitals. None of them caught covid during that time.

N95s work, if worn properly (and pass a fit test, even a crude one).

Obligatory story on Manchurian plague epidemic regarding how surgical mask come to be a standard requirement during the treatment of any airborne disease [1][2].

Mind you that the original surgical mask was not invented for surgery, it was invented for the treatment of patients with airborne virus. Heck, every.single.time you meets someone who are skeptical about the effectiveness of the mask in mitigating the airborne virus transmission, just send them this story [1][2].

It also interesting to note that the inventor of the surgical mask Dr. Wu, (the doctor mentioned in the article) is not even the resident of Imperial China at the time, even though he is the first Chinese medical doctor trained and graduated from the University of Cambridge. The last Empire of China or Qing dynasty who was originally come from Manchuria, had to hire the best medical doctor that they can find in order the save the citizens native of Manchuria, from the raging epidemic. Dr. Wu has come very close to get the Noble price in medicine back in 1935 due to his novel surgical mask invention.

[1]https://insightplus.mja.com.au/2020/15/dr-wu-lien-teh-hero-o...

[2]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4291938/

The Wu Lien-Teh mask is the precursor of KN95 masks, not surgical masks. See this:

https://de.m.wikipedia.org/wiki/Datei:How_the_gauze-cotton_m...

Surgical masks offer virtually no (personal) protection against airborne disease and fulfill a completely different purpose.

Based on the design and capability, I doubt Dr Wu original mask back in the pandemic was even close to N95 mask in filtering the air probably closer to the surgical mask of today, if not worst. The N95 as we know today was invented just recently in 1995[1]. Even with its rudimentary design, Dr Wu's mask had managed to save many lives back then, and in my opinion surgical mask of today will be similar if not better than the original Dr. Wu's mask design.

[1]https://en.wikipedia.org/wiki/N95_respirator

> Based on the design and capability, I doubt Dr Wu original mask back in the pandemic was even close to N95 mask in filtering the air probably closer to the surgical mask of today, if not worst.

Surgical masks are not designed to filter air, they are designed to prevent droplets from exiting the mouth and contaminating the surrounding - especially an open wound like you'd have during surgery. Hence, it's called surgical mask. They are loosely worn.

The Wu Lien Teh mask was designed to filter air - with the capabilities of the time. It was tightly worn. It would've been a far more effective filter than a modern surgical mask.

I am not convinced that Dr Wu's mask during the Machurian epidemic is closer to N95 quality than our surgical mask with various ASTM rated level 1, 2 and 3 standards. If you have any credible references with scientific evidences to the actual quality of his original mask, I'd genuinely like to know.

Personally I will take any protection that I could wear to mitigate and prevent the virus transmission to and from myself than using nothing, since Covid virus is known to be transmitted thru both airborne and bodily fluids including saliva[1]. Like they always mentioned "every little helps". There is also a popular old saying, "no rattan, roots will do" .

[1]https://directorsblog.nih.gov/2021/04/22/study-demonstrates-...

As suspected, it's exactly a probability game. If there's few infectious particles sure to low concentrations (e.g. people distance or are outdoors), you would roll the 70% penetration chance fewer times, and result in very few particles reaching deeper into lungs too as the velocities are reduced.

When very close to an active particle source, you'd roll the conditional probability dice many more times.

The critical number is the base infectivity or viability. (CFU essentially) It is expected that sub-viable numbers might even work as a kind of vaccination if people isolate long enough. (stay at home for prolonged time without contact - scale of days at least)

Yes. Crazy how hard it has been for people to get this:

Imagine a bulletproof vest with three larger-than-bullet-sized holes in it. Say you know someone is going to shoot ten bullets at you - would you not wear the vest because "the attack vector can fit through the pores"?

The point is people treat this as a binary 'safe' / 'not safe' switch, when actually risk is related to the distribution of exposure to dosage.

If we're talking about the size of the holes in a mask compared to a virus, then it would be more like wearing a "bulletproof" vest full of holes 10x bigger than a bullet.

But the area which does have coverage is still significant, right?

I guess it's a choice of analogy. If virus particles are like bullets, protection can be viewed as proportional. But if it's viewed more like a liquid, seeping through any hole, then only full watertight protection works. I'd argue that the reduced transmissibility we see from outdoor exposure supports the first of those as a more apt analogy.

There is no evidence that inoculation with sub-viable numbers of virions works at all as a kind of vaccination. It's an interesting hypothesis but no one has done the human challenge trials necessary to test it.

If high resolution video is to be believed, masks reduce how many particles get into the air when we cough, sneeze or talk.

https://www.youtube.com/watch?v=H2azcn7MqOU

For those of you who haven’t seen the slowmoguys video about talking with and without a mask this is good:

https://youtu.be/gZ66wJFD3bs

If you want to skip the technical lighting bits then jump to the 4 minute mark. It’s difficult to argue against footage like that and it makes you wonder why some people take off their masks to talk.

> wonder why some people take off their masks to talk.

Because voice is muffled by the mask and makes it very hard to understand in some cases. Taking off the mask is not acceptable, but it is not an unjustified response.

I was very happy to see "aerosols are physically defined as airborne solid or liquid particles with diameters smaller than 100 μm" as opposed to the bad 5 μm definition that caused so much trouble.

Have any studies been completed yet on immune system efficiency/suppression after covid restrictions (masks, hand sanitizer etc) ?

In Australia we were very lucky with the COVID situation. And purely annecdotal, but I know many people who haven't been sick at all during the pandemic. But as we approach winter here and perhaps no longer hand sanitize appropriately, many of these people are becoming "the most unwell [they] have been in years".

protip: shower once a month to train your immune system during lockdown

I don't think it works that way. Your kids might develop some new allergies if you sanitize them too much, but just rub some dirt on your face or eat sauerkraut or something, it'll work out.

In Japan, people that are sick wear masks, voluntarily, not to spread the infection. Well, that was my observation travelling Japan, anyway. I was amazed by it, and as the pandemic started last year, I had hopes that this thoughtful behavior will become a norm in my area too (central Europe).

Unfortunately, it seems that will not be the case. Masks are universally hated.

Wearing masks when sick is a good hygiene practice in general. But in COVID context with significant asymptomatic spread it won't help as much as it does for colds and flu.

I did not bother to read this thread in its entirety though I typically enjoy HN discussion.

Undoubtedly, masks of any quality work. Airborne viruses still exist in secretions (likely, in much higher concentrations). Secretions sometimes even carry living cells, would you imagine (in fact the #1 cause of sputum sample contamination for C&S; the bane of internists everywhere). High velocity events certainly increase the environment-load of secretion and thereby virus.

You don't need evidence in all cases. Im sorry to say, to the otherwise curious-minded, this is one of those cases.

This isn't a study; it is a mathematical model [1].

> Here, we develop a quantitative model of airborne virus exposure that can explain these contrasting results and provide a basis for quantifying the efficacy of face masks. We show that mask efficacy strongly depends on airborne virus abundance. Based on direct measurements of SARS-CoV-2 in air samples and population-level infection probabilities, we find that the virus abundance in most environments is sufficiently low for masks to be effective in reducing airborne transmission.

Meanwhile, they ignore the dozens of studies showing masks are ineffective, or even counterproductive:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/

https://pubmed.ncbi.nlm.nih.gov/29395560/

https://pubmed.ncbi.nlm.nih.gov/32590322/

https://pubmed.ncbi.nlm.nih.gov/15340662/

https://pubmed.ncbi.nlm.nih.gov/26579222/

https://pubmed.ncbi.nlm.nih.gov/31159777/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5779801/

https://pubmed.ncbi.nlm.nih.gov/19216002/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2493952/pdf/ann...

https://www.nap.edu/catalog/25776/rapid-expert-consultation-...

https://www.nap.edu/read/25776/chapter/1#6

https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6599448/

https://www.acpjournals.org/doi/10.7326/M20-1342

https://link.springer.com/article/10.1007/s00392-020-01704-y

you really had that list ready to go...

Yeah, this right here. Masks efficacy for stopping viral transmission has been heavily studied. I could post literally hundreds more examples of statistically significant, RCT'd science showing they have no effect on viral transmission.

Wearing masks has never been about the science.

> I could post literally hundreds more examples of statistically significant, RCT'd science showing they have no effect on viral transmission.

Please do. I'm only aware of about a half-dozen controlled trials of mask usage, and they're all low-powered.

Here's a meta-study of 10 you can peruse...

"In pooled analysis, we found no significant reduction in influenza transmission with the use of face masks (RR 0.78, 95% CI 0.51–1.20; I2 = 30%, p = 0.25)"

https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article

Interesting how some of the linked studies either contradict your statement, or seem to have nothing to do with it.

Some are indirectly related, but all are linked in some way. Like how some find that it _could_ have a positive effect and postulate how, but that the studies they reviewed in the meta-review didn't _show_ that.

The study about mask being ineffective is about cloth mask. That's why the hospital masks are no longer made of cloth.

That is true; but a large number of people are walking around with cloth masks believing that they are helpful, while that study has shown them to potentially increase risk.

It did show "Penetration of cloth masks by particles was almost 97% and medical masks 44%." So that was a positive for medical masks. Though some of the other studies address how those need to be used properly and not re-used.

The main point is that, in general, media has not done a good job of transmitting studies on risk reduction; they've mainly done propaganda, which can do more harm by promoting things like cloth masks and not informing people about proper use of medical masks.

The Vietnamese study found that cloth masks increased risk compared to medical masks, not compared to no mask. Confusingly, their control group also wore masks, just in fewer situations:

> Hospital wards were randomised to: medical masks, cloth masks or a control group (usual practice, which included mask wearing).

The first paper doesn't say what kind of mask the control participants wore, but a subsequent paper says only 38/458 control participants wore a cloth mask. I think the implication is that the rest wore medical masks, though neither paper ever says explicitly.

https://bmjopen.bmj.com/content/10/9/e042045

That subsequent paper is a subgroup analysis that should be treated with some care, but found comparable performance between medical masks and cloth masks washed in the hospital laundry. That suggests the problem was inadequate hand-washing, not the masks themselves.

There is zero evidence that masks increase incidence of disease compared to no mask. RCTs of mask use in public (e.g., DANMASK-19 and earlier flu studies) suggest that the benefit of the mask to the wearer--excluding the benefit of the mask to others nearby from source control--is less than a 50% reduction in disease, with a 95% confidence interval centered somewhere around 20% but including zero. The RCT evidence says nothing beyond that.

Public health authorities have indeed spoken with unjustified confidence as to the efficacy of masks. You're doing the same thing here in the opposite direction, though. Given the information above, can you correct your comment?

That study also focuses on influenza which does not transmit quite the same way as COVID. A bunch of these links were the same thing being shared in the early days of COVID by doctors claiming that masks did not work. Obviously most healthcare organizations have changed their recommendations in light of new evidence specific to this pandemic.

There doesn’t seem to be any evidence specific to this pandemic that masks work. The CDC study released recently puts it at 2% or so. And there was no new evidence in March that caused the reversal from “masks don’t work” to “you must mask up” to “two masks are better”.

Obviously there was a reason for them to change their recommendations, but it is not evidence, and might not even be health related - I know someone who was involved with a recommendation in a national organization, and a big part of it was “instilling a feeling of pandemic”.

You are exactly correct, and being downvoted because of religious zealotry. This is a mathematical model. Yes, face coverings cover the face. It's a long (and ultimately disproven) leap to: face coverings materially suppress virus in a society of millions of people.

Half the articles on your list are tangential (masks make it marginally harder to exercise, ok duh). The article posted helps us understand why the viral concentration in the environment also impacts efficacy, it helps explain why some of the articles you posted see inconclusive results.

And even the "masks make it marginally harder to exercise" is likely wrong.

The winner of the 10,000m race at the 2019 USA Track & Field Championships wore a mask against his pollen allergies. [1]

Worn properly, they just disappear. I wear N95s a work for many tasks, and they are mildly distracting for a few minutes, then I forget about them. Even more so now with wearing them for the pandemic.

Yes, education about masks could be a LOT better, but using that is more anti-mask FUD is borderline sociopathic.

[1] https://www.oregonlive.com/trackandfield/2011/06/galen_rupp_...

According to that article, the winner of the 10,000m race wore a mask to protect against his allergies for the first 4,000m, by which point it was just too uncomfortable to continue wearing: "Rupp said Salazar told him to “wear it as long as you can. As soon as it starts to get real hot or uncomfortable, or starts to stick and get sweaty, throw it off.” The mask came flying off after 4,000 meters. But Rupp was content to bide his time until the 9,200-mark."

Right, and during that time, he was respirating at around 20X the rate of you or I sitting here.

1 MET, or Metabolic Equivalent Task, is about 3.5 mL of oxygen per kilogram per minute, which is roughly equivalent to the energy expended when sitting quietly. [1]

The Vo2max of high-level athletes runs up to 97.5mL/kg [2]

Sure, he used it for 'only' 40% of the race.

In a national championship where fractions of a percent of O2 uptake make the difference in winning.

The point is that he still wore it, running in the pack of a national championship, for nearly two and a half miles (400m=2.585mi), over 11 minutes, respirating at a level that you literally cannot imagine if you can post that comment.

The mask neither slowed him enough to take him out of contention, nor did it create sufficient oxygen debt that he could not win.

IOW, the mask had a completely marginal effect at levels of respiration more than an order of magnitude beyond any ordinary activity.

Moreover, since air resistance increases roughly with the square of velocity, a first approximation of any mask drag or throttling he experienced vs normal respiration is not 20X, but more like 400x what a normal person would experience.

And even your own citation points to it being "uncomfortable, sticky or sweaty", in the context of a national championship race, not being any kind of oxygen hinderence.

And yet you want to claim that this can be ignored because he didn't wear it the whole time.

So, yes, everyone knows that masks can be mildly uncomfortable, even during exercise. But they are a helluva lot less uncomfortable than enduring that respiratory/vascular disease, and a lot more ethical than spreading it.

[1] https://en.wikipedia.org/wiki/Metabolic_equivalent_of_task

[2] https://www.topendsports.com/testing/records/vo2max.htm

You really hurt your credibility when the first link doesn’t support the argument you claim it does.

Here is a recent published review for those seeking a more comprehensive and complete evaluation of the literature:

Howard, Jeremy, et al. "An evidence review of face masks against COVID-19." Proceedings of the National Academy of Sciences 118.4 (2021).

https://www.pnas.org/content/118/4/e2014564118

That is a joke of a “review”, and should never have been published.

Consider that it doesn’t mention the only randomized controlled trial of masks and Covid ever performed (it showed no significant protective effect), which was conducted during the period the “review” was being compiled:

https://www.acpjournals.org/doi/10.7326/m20-6817

There’s simply no excuse. the authors cherry-pick and misinterpret top-line data to craft a narrative. It’s not a review, it’s an editorial.

I'm not familiar with that study, but I think it's important to note that the PNAS article was submitted mid-2020, so it's hard to understand your criticism here.

You should note well that the study you point out made no assessment of whether mask wearing reduced the risk of spread from the mask wearer to others, which is a key point of the utility of mask-wearing during this pandemic.

It is very deceptive for you to claim that this is the only trial of “masks and COVID” when you omit that nuance.

> Meanwhile, they ignore the dozens of studies showing masks are ineffective, or even counterproductive

Let's try to figure out how well your summary is actually supported by your citations, especially as TFA is about medical masks and N95 masks and doesn't mention cloth masks.

TL;DR: It's not (and ignores the multiple studies showing surgical and N95 masks are effective to prevent SARS-CoV infections).

What your citations say is "cloth masks seem ineffective (but not surgical/N95), masks in general seem to protect less from influenza than coronaviruses, and wearing a mask may have some effect on exercise (although magnitude of the effect and consequences are unclear)". I wouldn't have had a problem with that statement. Whether that's the whole story or cherry-picking of studies is another question.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/

(2015) Shows that cloth masks are less effective than medical masks... and incidentally that medical masks are effective. One study in, already contradicts your statement.

https://pubmed.ncbi.nlm.nih.gov/29395560/

(2017) Not about mask efficacy in disease prevention, but effects on exercise. No difference in distance, heart rate, O2 saturation, but 20% higher shortness of breath.

https://pubmed.ncbi.nlm.nih.gov/32590322/

(2020) Not about mask efficacy in disease prevention, but effects on exercise again. Also, not an experimental study but a comment/hypothesis.

https://pubmed.ncbi.nlm.nih.gov/15340662/

(2004) Not about mask efficacy in disease prevention, again. Study on patients with end-stage renal disease.

https://pubmed.ncbi.nlm.nih.gov/26579222/

(2015) Not about mask efficacy in disease prevention, again. Study on pregnant women.

https://pubmed.ncbi.nlm.nih.gov/31159777/

(2019) First interesting one. Show that viruses may deposit on the outer surface of medical masks. May prove useful in educating people to handle with care (although it seems that contamination by touching contaminated surfaces accounts for a negligible amount).

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5779801/

(2012) Ah, better. Review of a small number of other studies, focused on influenza and close contact with an infected patient. Does not conclude masks are ineffective, but more that good data and studies are hard to come by, that the studies they reviewed were between inconclusive and positive, and they may be protective when combined with other hygiene practices. Also notes that the studies on SARS coronavirus transmission found masks protective, but the results may or may not apply for influenza. It also notes compliance and correct usage are likely factors in reduced effectiveness.

So, while this is the closest so far to your assertion, it doesn't quite support it either. Annex 5 in particular shows that the SARS coronavirus studies reviewed seem to show a protective effect.

Much larger and wider reviews, that include this one, reach different conclusions for the topic at hand. See for example https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8084286/ and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7718106/

https://pubmed.ncbi.nlm.nih.gov/19216002/

(2008) Lol. Study on 32 health-care workers, and the incidence of common cold. There was 1 cold in each group. Sample way too small to reach any conclusion, as they themselves conclude.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/

Same article as the first one in the list.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2493952/pdf/ann...

(1981) Interesting, although a small trial study. But it only cares about a very specific thing: the efficiency of masks in surgery to avoid contaminating an open wound, unrelated to the airborne spread of respiratory diseases. More studies and reviews have followed, with mitigated results, see for example https://pubmed.ncbi.nlm.nih.gov/33039336/

Interesting but irrelevant for the topic at hand.

https://www.nap.edu/catalog/25776/rapid-expert-consultation-...

(2020) Expert consultation, limited to the effectiveness of homemade fabric masks. It says verbatim: "It does not apply to either N95 respirators or medical masks." (and it doesn't even conclude that homemade cloth masks are ineffective, only that more research is required).

https://www.nap.edu/read/25776/chapter/1#6

That's the same as the article just above. Could be the 2nd honest error of course, or could be a sign you've copy/pasted part or all of the list with little editing/proofreading.

https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article

(2020) Review of multiple measures against influenza contamination, that seems to show no effectiveness. The authors point out themselves the limitations of the study however, small sample size and compliance issues. It's an interesting data point, but it targets influenza and I wouldn't say it disproves masks effectiveness.

When looking at the bigger picture, and more and larger review, doesn't yield the same conclusions. See for example https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7718106/ that includes this study among those reviewed. Interestingly, it seems to show much more conclusive results for coronavirus infection prevention than influenza, and cautions against cloth masks.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6599448/

(2019) Physical study of filtering efficiency of cloth masks vs surgical masks, especially after washing

https://www.acpjournals.org/doi/10.7326/M20-1342

(2020) One of many physical studies on patients coughing in a petri dish with various mask types. Only 4 patients, and one of the only such physical studies I've seen that didn't show a significant effect.

https://link.springer.com/article/10.1007/s00392-020-01704-y

(2020) Another one that talks about exercise and not infection.

---

Looking in general at country-level data, using masks earlier seems to be significantly associated with lower mortality. See for example https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7695060/ for a wide study and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7392429/ for a small comment

We know masks work for infection control which is why they are used in hospitals and also in clean room style manufacturing.

Bacteria and viruses behave differently. It’s possible, even likely, that a measure against one will be ineffective against the other.

In an attempt to fights a specific virus, namely sarscov2 - no, we don’t know that masks work. The cdc numbers I saw talk about 2% reduction in vivo.

Anecdata from a _very_ frequent flyer: Naomi Campbell’s Airport Routine (2019). Makes sense to me.

https://youtu.be/b-U_jT9qWvs

...in hamsters? In mice?

No, in a mathematical model - the gold standard of junk science.

The VAST majority of mask wearing I have seen in California has been average cloth-covers. I have only seen a handful of people out of thousands actually wearing N95 masks, so perhaps N95 is highly effective at stopping viruses, but I see basically nobody wearing that. Stores, offices, buildings, all are completely fine with you wearing a bandana over your face. There is effectively no point in even mandating mask laws unless you actually mandate the TYPE of mask that must be used. The coffee filters people are wearing over their face will do close to nothing, if not even make everything worse for their own personal health (lung issues, bacterial infections, etc.)

I've never seen anyone wearing a coffee filter over their face. What are you talking about?

I haven't either but I did have to drive several miles out of my way a few months ago to get coffee filters at the only store in the state that seemed to have them in stock. I was told during checkout people were buying them in bulk to use as masks.

Or buying them in bulk... to make coffee? I'd assume that if people are working from home, they're also making coffee at home instead of getting it at work or on the way to work. And that would be a pretty reasonable explanation for shortages of filters that fit in home coffee makers.

I know my personal use of coffee filters went up about 10x during the pandemic. And no, they were not on my face.

I would think a paper filter filters a lot better than cloth at least. The problem is breathing through it of course (as opposed to around). I searched and see some projects on the internet where people are trying to use them. Seems like a worthwhile idea to me.

>The coffee filters people are wearing over their face will do close to nothing

I'm not an expert, but I believe this is not quite accurate. As I understand it, even a piece of cloth helps prevent the spread of the virus to others. The mechanism is that the virus exits your nose/mouth in the form of macroscopic droplets that later break down into microscopic droplets a few inches from your face. A bandanna will catch the big droplets before they split apart.

Is there some global increase in lung issues (besides covid) or bacterial infections or something?

The other thing to consider is fit. When I needed a mask for workplace safety, I had to get a fit test done - otherwise you leave massive gaps around the edge of the masks that lets unfiltered air in and out.

I think surgical masks do a good job in containing droplets from a cough or sneeze, but if there are airborne particles, I doubt they do much. A good fitting N95 probably helps in that department.

Even if this is true, I still don’t think someone at high risk should be trusting their life to a piece of cloth.

We are in pandemic-mode for over a year now - isn't it obvious that masks help by now?

“... is still under debate ...” - NEXT!

>Surgical masks with particle collection efficiencies around ~50% cannot prevent the release of millions of particles per person and their inhalation by others (green dots in Fig. 1, B and D). In other words, the human-emitted respiratory particle number is so high that we cannot avoid inhaling particles generated by another person even when wearing a surgical mask

So the entire premise of the modeling in the paper rests on the assumption that surgical masks can filter some percentage of viral particles. It's my understanding that viral particles are around 3 orders of magnitude smaller than the pores in surgical masks. So is there any evidence that surgical masks can filter aerosolized viral particles?

Viral particles are concentrated in droplets and aerosols, which are significantly blocked by surgical masks.

Virus particles do not travel naked in the air, instead they are colloidally suspended in liquid, both droplets and aerosols.

So, if your filter catches the droplets and aerosols, which are much larger in size than the actual virus, the filter works.

Realization that somebody's droplets are getting into your mouth and nose makes one want to wear mask even after pandemic is over :)

You may want to check how much of your body weight is bacterial and how easy it is to exchange samples with others. Just own the things that make us human.

You're of course free to do whatever you think makes sense, but please don't expect other people to follow. The world is full of risks, but everything is a tradeoff - it's really bad if we start thinking random people are a danger to us.

And for what it's worth, I'm not anti-mask in the context of the pandemic - I've been wearing masks indoors since the whole thing started and I'll continue to do this until most people around me are vaccinated, for their sake.

Except that field data shows they don’t because they are not used precisely as required - which means the filter doesn’t work effectively if at all and then it becomes infectious waste that isn’t treated and disposed of correctly.

Human system effects dominate - as the field data shows. It’s like HCQ - works in a lab, not in the real world.

Might be useful in tightly controlled medical settings with adequate filtered ventilation. But there’s no hard evidence beyond that at this stage.

Feynman’s rule still applies.

assuming: 1) 100% capture of air flow 2) no fatigue (ie capture is same at t=0, and t=later)

anyone with glasses will tell you 1 isn't a very good assumption. As masks saturate in moisture, back pressure causes (1) to be more false.

Science is based a lot on assumptions and beliefs. A scientist who does not consciously say: „We have observed that… which makes us believe that…“ still ultimately becomes a victim of his unconsciously formed belief system, a pseudo-religion.

I’m a software engineer, I work scientifically, but I don’t own the truth. I own the thought process which works on top of assumptions. But I don’t want my own work to feel like magic, and to avoid that, I observe and try to understand it. But at the end of the day I have to say: „I assume that my program is bug free because I have observed many test runs in which the program behaved correctly. I belief it will work well at the customer.

Same has to be said for above study. Otherwise we wouldn’t find studies which even claim the opposite. These other studies are just based on different assumptions and belief systems.

Here’s a nice interactive graphic showing how masks block particles:

https://www.nytimes.com/interactive/2020/10/30/science/wear-...

That's a very cool visualization and I wish I'd seen it before. I am curious though as to what makes some viruses have higher R values than others. These masks more effectively stopped influenza and I still don't understand why.

Google cross-protection and competition in respiratory viruses. Lots of pre-2019 literature.

"in our specific model which we specifically created around the exact conditions required for them to work"

Results only apply to indoor environment. Maybe source control could be extrapolated to outdoor conditions and close contact.

Doesn't seem to have been effective here, we have had to wear them including outdoors since October. But give me some model over real world data to convince me.

Aren't masks mostly/also about decreasing the area of the air that you pull in (closer to you, or in other words the distance from which you pull is smaller)?

like take a piece of paper in front of your face and breath with mask and without

No. https://www.youtube.com/watch?v=0Tp0zB904Mc

Masks work by trapping particles exhaled or inhaled.

A science study that only shows, as this one does, that face coverings cover the face is not very useful. The public policy piece is much more complex. High masking states did NOT do better on COVID than low masking states.

By what metric? By deaths per capita, my impression was the low masking states did worse, but I didn't rigorously check the data.

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