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Comment by eric_b | Hacker News Reader

How can you write so many words defending the CDC? Their "guidance" is based on cherry picked science at best, and gut feelings and political narratives at worst. There are plenty of studies that suggest lockdowns, closed schools and other "mitigation" efforts are ineffective or net harmful, but eh, just ignore those right?

Look at the most recent issue of vaccine boosters. The FDA panel of experts (whom we're supposed to trust now, right?) said boosters are not necessary. CDC comes in and says the FDA is wrong, boosters are good jk lol. What a joke.

Can you point me to a well done study on cloth masks and their efficacy? 19 months in and I have yet to see one. But people "feel" that masks must work, so CDC guidance says wear them. Surely at this point we should have so much compelling data about masks if they are effective...

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> Can you point me to a well done study on cloth masks and their efficacy?

I'm guessing you've hidden away a lot of meaning in the words "well done" but here's one:

https://www.preprints.org/manuscript/202004.0203/v4

These also: https://docs.google.com/document/d/1HLrm0pqBN_5bdyysOeoOBX4p...

If you don't think these are "well done", can you at least clarify what such a study would look like and point us to an example?

Slipping in here with a question that will probably seem obnoxious, but isn't intended so.

If cloth masks are effective (I'm not arguing either way) and those who wear them felt endangered by those who don't, could they simply double their mask? Particulates passing in or out, in either direction, would be subject to the same amount of material as if both were wearing a single mask.

guy with mask + guy with mask = two masks

guy with 2 masks + guy with 0 masks = two masks.

I'm not suggesting that anyone should have to bear the responsibility of another, but the effect should be the same for the wearer if non airborne contaminated surfaces are of low risk. Unless it's a matter of directionality.

Could it be tested to observe a controlled situation where group A) exhales only through cotton while inhaling without, while a seperated group B) does the opposite, exhaling without and inhaling with?

Is this absurd to consider? I'm not feeling well and might actually be absurd right now.

I think part of the benefit of everyone wearing masks is that there is more value in limiting the distribution of virus laden particulates from the source, ie the infected persons mouth or nose, at least to an extent. That is best done when an infected individual has a mask on. Additionally, if we assume that wearing a mask limits spread, then unmasked individuals overall are a higher risk for receiving infection. Therefore community risk is higher.

That's how we end up with a calculus that determines that impinging individual liberty (requiring masks) has a net benefit (limiting overall community spread).

I guess a similar analogy might be: driving half the speed limit might in a weird sense feel like you're protecting yourself from harm in an accidental if else someone drives too fast, but the better policy would be that both directions of traffic maintain speed at or under the limits. Again, this is an instance where we limit individual freedoms when there is a perceived net benefit to community safety.

That's actually a good question and has to do with the physics of respiration. When you inhale, you're creating negative pressure that pulls particles closest to you into your lungs, leaving a void that other particles fill as they randomly redistribute themselves. This causes aerosolized droplets to follow the path of least resistance around the mask, as if they are pulled, rather than landing against it. That's why real N95/100 masks require a proper fit: if there's even a sliver of space between the mask and face, inhaling will simply suck air in through that space instead of through the filter, which has a higher "resistance".

When you exhale, on the other hand, you create positive pressure which violently expels the droplets regardless of what's in the way. This creates droplets with high velocity and turbulent flows within the mask that prevent them from traveling a straight path through the mask and cause most of them to collide with the fabric.

Basically, once it's exhaled it's a hazard to anyone who doesn't have a properly fitted N95/100 mask (which requires specialized equipment, though it's relatively common)

Those guys who used to say 2+2=5 might have been on to something, but more correctly, it was probably 3 for fluid dynamics here.

I remember as an OTR driver the truckstop bathrooms I survived each day. The olfactory violence was palpable enough to feel it crawling through the mask and see it grinning as it coursed through what must have been an unusual ratio of gas to air. I'd think to myself in that sometimes surreal environment where photons seemed to sweat and stagger, that even an n95 was pointless, perhaps life itself. If rona be here, every particle is riding a pale horse in a hazmat suit. I'll always consider myself a permanent petri dish for that.

I'd be all for mandatory toilet skirts.

The idea is that the masks filter particulates at the source, and then again at the destination. See https://www.livescience.com/face-mask-visualization-droplets... for a visualization. Reasonable. Wearing masks when having symptoms is elementary courtesy, and self quarantining is even better. Unfortunately we've embraced the 'asymptomatic spreader' idea a bit too much and now we regard anyone that doesn't take the most extreme measures at all times as a de facto murderer, because there might be a tiny chance they are infectious. Not healthy.

Stocks vs. flows. The idea is that masks reduce the flow into a reservoir (like inside air of a building), and not just direct transmission. In your example double masking might reduce your personal intake from a large reservoir (refilled by unmasked people who happen to be sick), while everyone wearing a mask should reduce the size of the reservoir.

https://youtu.be/Y47t9qLc9I4

this minutephysics video might answer your question

Solid math and reasonable general principles, with an element or two I question. He comes close to clarifying it, though not quite. And while the percentage of 50 was a disposable placeholder to illustrate valid points, I doubt cotton could be quite so effective as 50% leading to 75% (and certainly not 100%) and some assumptions are required to flow along with the logic, as was mentioned. This is still reasonable for a fast-paced video; some finicky details must be overlooked. However, it is primarily based on math and no data was shown giving any unambiguous indication for cotton efficacy. Also, he addresses directionality as nearly equal for the illustration, but later provides another resource that accounts for it in detail. Was this prefactored? Otherwise surprisingly apropos and worthwhile.

Thank you

you’re welcome. i’m a bit low on sleep so i missed part of your question, and don’t think the video addresses it — that is, are two [cotton] masks more effective than one. i honestly think that this is an interesting question. for most people, their intuition would be to answer “probably,” but i suspect there are some complexities that someone smarter than i am would have to address.

wearing two masks instead of one wouldn’t make things worse, though. but better? again, good question.

Biggest mask study so far:

https://med.stanford.edu/news/all-news/2021/09/surgical-mask...

Cloth masks don't work at all, and surgical masks only reduce infections by 11%. N95s are probably a lot more effective but this study didn't measure those.

"Look at the most recent issue of vaccine boosters. The FDA panel of experts (whom we're supposed to trust now, right?) said boosters are not necessary [for the general public (https://qz.com/2061783/why-the-fda-panel-says-most-americans...)]. CDC comes in and says the [boosters are available for some groups (https://www.cdc.gov/coronavirus/2019-ncov/vaccines/booster-s...) based on the recommendations of the FDA panel]."

The problem with getting your science news from FB memes is that some nuance tends to get lost.

"Studies show that after getting vaccinated against COVID-19, protection against the virus may decrease over time and be less able to protect against the Delta variant. Although COVID-19 vaccination for adults aged 65 years and older remains effective in preventing severe disease, recent data pdf icon[4.7 MB, 88 pages] suggest vaccination is less effective at preventing infection or milder illness with symptoms. Emerging evidence also shows that among healthcare and other frontline workers, vaccine effectiveness against COVID-19 infections is decreasing over time. This lower effectiveness is likely due to the combination of decreasing protection as time passes since getting vaccinated (e.g., waning immunity) as well as the greater infectiousness of the Delta variant.

"Data from a small clinical trial show that a Pfizer-BioNTech booster shot increased the immune response in trial participants who finished their primary series 6 months earlier. With an increased immune response, people should have improved protection against COVID-19, including the Delta variant." (https://www.cdc.gov/coronavirus/2019-ncov/vaccines/booster-s..., https://www.cdc.gov/vaccines/acip/meetings/downloads/slides-...)

https://www.thelancet.com/journals/lancet/article/PIIS0140-6...

The FDA panel and the CDC approved it for the same exact sets of people. Where are you getting your news from?

https://twitter.com/ggreenwald/status/1441399817045958657 which references: https://www.nytimes.com/2021/09/24/world/covid-boosters-vacc...

SCIENCE! or whatever agenda the current administration wants to push. This was the same reason all these "leaders" (including Joe and Kamala) were telling everyone to be skeptical of the jab previously, because "you can't trust the orange man's CDC and the vax he pushed through so fast!"

Big tech Co is pushing a bigger agenda and silencing dissent.

Greenwald used to be great but has turned into an alt-right shill at this point. He's intentionally not talking about the FDA panel and hiding that in his tweets, and neither does your NYTimes source.

They're talking about a different CDC committee that went against the FDA panel, and the CDC director sided with the FDA panel(which meant going against one recommendation of the CDC panel). So yes, you and Greenwald blaming the CDC for siding with the expert FDA panel.

This kind of misinformation spread on the right is insane and permeates every discussion. It's easier to spread misinformation than to fight it, this is such a sad state of affairs.

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