Masks are effortless, but there is also a lot of reason to believe they are not nearly as effective as was sold to people in the early summer.
At some point we get into "just wear a crucifix to ward off the Devil" territory of superstition.
Masks are obviously helpful at preventing transmission of some illnesses, but I've seen enough evidence that Coronavirus spreads via aerosol to not really trust the things.
Mayeb you can post some (preferably peer-reviewed) literature links that show "a lot of reason" to believe this.
> 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.
> The recommendation to wear surgical masks to supplement other public health measures did not reduce the SARS-CoV-2 infection rate among wearers by more than 50% in a community with modest infection rates, some degree of social distancing, and uncommon general mask use. The data were compatible with lesser degrees of self-protection.
I don't think any public health experts are saying "wear a mask and you'll be safe", they're saying "if everybody wears a mask, that will slow the infection rate". A study of a community with "uncommon general mask use" does not dispute this.
Finally, I don't think it's clear that a randomized controlled trial is the best method to answer this question. Aside from ethical concerns, you can't give someone a placebo mask. Shouldn't we assume that people will behave differently when they're wearing a mask?
"Although the difference observed was not statistically significant, the 95% CIs are compatible with a 46% reduction to a 23% increase in infection."
The points you are raising about limitations in no way affect the conclusion of the work. Short of putting infected people in a room with uninfected people, there is no ethical way to test the hypothesis that "masks could decrease disease transmission from mask wearers to others".
But since it's pretty unlikely that masks are effective in one direction only, this is the highest-quality evidence we have that they have no effect in one of the two directions.
> Finally, I don't think it's clear that a randomized controlled trial is the best method to answer this question.
A randomized controlled trial is always the gold standard for an intervention of this sort. But yeah, you can't do one for that hypothesis. So you're stuck with something that is fundamentally un-falsifiable. The best you can do is try to do what people have done so far: look at populations, and see if mask mandates make any difference, or ask people who caught Covid if they wore masks, or do similar things within families.
This is called retrospective cohort analysis, and it is low-quality evidence, at best.
> Aside from ethical concerns, you can't give someone a placebo mask. Shouldn't we assume that people will behave differently when they're wearing a mask?
Yes, we should assume that this might happen. It could well be true that wearing a mask makes people be more careless about distancing, for example. This is called "risk compensation", and is a well-known phenomenon in public health.
1. do masks inhibit production of and exposure to aerosols carrying SARS-COV-2? This seems (to me) to me clearly established, and essentially irrefutable.
2. do mask mandates reduce the spread of COVID19? this is an entirely different question, and has almost nothing whatsoever to do with the abilities of masks referenced in (1) above.
Aerosols? It's far from established. In fact, it's a dubious claim, unless you're far more specific about what you mean by "masks". The best laboratory studies show that properly fitted respirators (i.e. as used in hospitals), can reduce aerosol emissions. But few people are wearing respirators, and essentially nobody is fitting them correctly.
Cloth masks? Surgical masks? Cup masks? About the only claim you can make is that they might reduce heavy droplets and then, only by about 30% or so. There's no reason to believe they have any effect on aerosol emission.
Michael Osterholm covered this extensively:
https://www.cidrap.umn.edu/covid-19/podcasts-webinars/specia...
Anyone who has done a mask fitting -- where they put you in a room with vaporized stuff that you can taste to detect leaks -- will tell you how difficult it is to get an aerosol-resistant seal on a mask. The chances that the general public is doing it is 0%.
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Data regarding the “real-world” effectiveness of community masking are limited to observational and epidemiological studies.
* An investigation of a high-exposure event, in which 2 symptomatically ill hair stylists interacted for an average of 15 minutes with each of 139 clients during an 8-day period, found that none of the 67 clients who subsequently consented to an interview and testing developed infection. The stylists and all clients universally wore masks in the salon as required by local ordinance and company policy at the time.
* In a study of 124 Beijing households with > 1 laboratory-confirmed case of SARS-CoV-2 infection, mask use by the index patient and family contacts before the index patient developed symptoms reduced secondary transmission within the households by 79%.
* A retrospective case-control study from Thailand documented that, among more than 1,000 persons interviewed as part of contact tracing investigations, those who reported having always worn a mask during high-risk exposures experienced a greater than 70% reduced risk of acquiring infection compared with persons who did not wear masks under these circumstances.
* A study of an outbreak aboard the USS Theodore Roosevelt, an environment notable for congregate living quarters and close working environments, found that use of face coverings on-board was associated with a 70% reduced risk.
* Investigations involving infected passengers aboard flights longer than 10 hours strongly suggest that masking prevented in-flight transmissions, as demonstrated by the absence of infection developing in other passengers and crew in the 14 days following exposure.
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Taken from: https://www.cdc.gov/coronavirus/2019-ncov/more/masking-scien...
All of these studies were conducted on data from the spring, when cases were declining across the northern hemisphere. How are these places doing now?
DC: up dramatically
https://covid-19.direct/metro/DC
Canada: all-time highs
https://www.worldometers.info/coronavirus/country/canada/
Germany: all-time highs
https://www.worldometers.info/coronavirus/country/germany/
US nationally: all-time highs
California: all-time highs
https://covid-19.direct/state/CA
New York: up dramatically
https://covid-19.direct/state/NY
Boston (where the "unified hospital system" was located): near all-time highs
https://covid-19.direct/metro/Boston
I could go on.
Anyone who attempted to conduct a similar analysis today would have to credibly conclude that masks have no protective effect whatsoever. But who knows...maybe they slightly alter the slope of the curve. It's impossible to tell without a controlled trial.
The german paper is particularly ironic, given that it was published approximately concurrently with a huge increase in diagnosed cases in the same city, which is now at all-time highs for the year:
Absolutely not the case. It would be just as credible, as has been noted by others in the comments here, to suggest that the major cause of spread is unmasked private gatherings.
> But who knows...maybe they slightly alter the slope of the curve. It's impossible to tell without a controlled trial.
I agree that without controlled trials, it is very difficult to tell definitively. That does not, however, translate into "there are lots of reasons to doubt ..."
https://www.acpjournals.org/doi/10.7326/M20-6817
Infection with SARS-CoV-2 occurred in 42 participants recommended masks (1.8%) and 53 control participants (2.1%). The between-group difference was −0.3 percentage point (95% CI, −1.2 to 0.4 percentage point; P = 0.38) (odds ratio, 0.82 [CI, 0.54 to 1.23]; P = 0.33). Multiple imputation accounting for loss to follow-up yielded similar results. Although the difference observed was not statistically significant, the 95% CIs are compatible with a 46% reduction to a 23% increase in infection.
“ Although the difference observed was not statistically significant, the 95% CIs are compatible with a 46% reduction to a 23% increase in infection.”
Also, I quoted this exact line in a comment below, so I'm not sure how you can credibly claim that I'm "mis-representing" something.
Imagine you are standing close to someone at a party who starts talking to you. You immediately notice their bad breath (~aerosols). Now imagine they are wearing a mask, then imagine you both are. How much of the bad breath would you still notice in each case? That's the effect of masks.