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Comment by tlogan | Hacker News Reader

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Surgical masks do reduce the spread of COVID-19, and even cloth masks reduce symptoms of respiratory illness. [1] During an emergency, we have to act. It's absurd to expect that we should wait for a huge study to confirm what we we already know about respiratory viruses in general. In a low-info environment, the prior is clearly to favor mask mandates. And it turns out, it was the right call!

[1] "Surgical masks reduce COVID-19 spread, large-scale study shows" https://med.stanford.edu/news/all-news/2021/09/surgical-mask...

Let's be clear on the limits of the study you're quoting -- the total effect size was a tiny, tiny fraction a percent for the surgical mask arm (.09%), and barely reached a reasonable level of statistical significance (p=0.043). There was no statistically significant effect size for cloth masks.

No matter how you look at this study -- if you actually read it [1], and don't just read press releases -- it was not a strong result. Moreover, after the raw data for the study was released, there were a number of legitimate critiques that call into question the primary result. For example, this one [2]:

> In this short note we re-analyze the data from this trial using standard non-parametric paired statistics tests on treatment/village pairs. With this approach, we find that behavioral outcomes like physical distancing are highly significant, while the primary outcome of the study is not. Importantly, we find that the behavior of unblinded staff when enrolling study participants is one of the most highly significant differences between treatment and control groups, contributing to a significant imbalance in denominators between treatment and control groups.

Even if we accept the claims of the original paper at face value, the fact that you're citing this study as some kind of definitive rebuttal is, deeply ironically, a perfect example of the OP's critique: the highest quality evidence for mask mandates is simply and objectively weak, but most casual observers believe the opposite to be true.

Public health has exaggerated (or outright lied about) evidence quality throughout the Covid-19 pandemic. Is that the reason for this Polio event? Likely not, but if we're casting about for secondary or tertiary reasons, a drop in trust in public health due to their own trivially falsified propaganda wouldn't be the worst place to start.

[1] https://www.poverty-action.org/sites/default/files/publicati...

[2] https://arxiv.org/abs/2112.01296

I’d like to second timr’s remarks on that study. I’ve read the whole thing twice, and I found it to be low quality and tendentious: they didn’t even fairly present the results they did have.

It may be that the “surgical” masks they used, while not N95, had an electret layer. That would make them a lot better than the “procedure” masks commonly worn in the US against COVID.

Do you have evidence that asymptomatic people are even contagious? At the start of the pandemic there was a Pew survey that showed that 10% of people who know they have covid would still go to work. I think stuff like that explains the spread a lot more than lack of masking by non-sick individuals. Not everyone can afford to quarantine.

18 Nov 2020 "Research early in the pandemic suggested that the rate of asymptomatic infections could be as high as 81%. But a meta-analysis published last month1, which included 13 studies involving 21,708 people, calculated the rate of asymptomatic presentation to be 17%. ... Byambasuren’s review also found that asymptomatic individuals were 42% less likely to transmit the virus than symptomatic people." (https://www.nature.com/articles/d41586-020-03141-3)

7 Jan 2021 "The baseline assumptions for the model were that peak infectiousness occurred at the median of symptom onset and that 30% of individuals with infection never develop symptoms and are 75% as infectious as those who do develop symptoms. Combined, these baseline assumptions imply that persons with infection who never develop symptoms may account for approximately 24% of all transmission." (https://jamanetwork.com/journals/jamanetworkopen/fullarticle...)

How do masks not help curb the spread of a virus? Do you have any supporting literature on that matter?

Properly fitted N95s help a lot. Procedure masks, which are the type normally worn against COVID, do very little, especially since they are usually worn incorrectly. Other cloth masks do less than nothing, because they provide a false sense of security.

As you know, virus particles are too small to be stopped by the openings in the mask (which allow you to breathe). They are airborne, like smoke.

N95 masks have an electret layer which is made by blow molding fiber against a charged target. The result is charge embedded in the fibers. The charged fibers attract and hold the virus particles.

It would be possible to add an electret layer to a surgical mask, but it seems that this isn’t generally done, probably because they fit so poorly. Maybe someone here could speak to that.

Look at N95 on Wikipedia. The EU has required N95 on transportation for some time.

The Bangladeshi study mentioned in this thread might have used something like that (it isn’t clear from the paper and the promised paper on what kind of surgical mask they used hasn’t appeared yet).

Bottom line: the masks commonly used in the US over the past two years do virtually nothing, unless someone is coughing. How many coughing people have you seen in panic lately?

It's far from perfect, but I believe this to be the best RCT we have on masks out of Bangladesh: https://www.science.org/doi/10.1126/science.abi9069

We found clear evidence that surgical masks are effective in reducing symptomatic seroprevalence of SARS-CoV-2. Although cloth masks clearly reduce symptoms, we find less clear evidence of their impact on symptomatic SARS-CoV-2 infections, with the statistical significance depending on whether we impute missing values for nonconsenting adults.

I don't believe we have any good studies out of the US or Europe. There's a discussion about this and more on the Econ Talk podcast this week: https://www.econtalk.org/vinay-prasad-on-the-pandemic/

See my remarks:

https://news.ycombinator.com/item?id=32195416

There's for sure some youtube account which is taken as definitive and sufficient proof by some.

I've seen this: https://arxiv.org/abs/2112.01296 but I'm not qualified to really interpret it

> They still (to this day) did not acknowledge that vaccines and mask mandates do not limit spread of COVID.

They don't "acknowledge" that because it is not a true statement. Masks do limit spread of COVID-19. So do vaccines. Neither one prevents it completely, but that's different from "do not limit spread", and at no point was there either scientific or public health consensus that either one would completely prevent spread.

> Yes - at very beging the assumtion was that vaccines will limit COVID spread but that is not true any more for BA variants

Vaccines still do limit COVID-19 spread, even for the latest variants. They do not prevent it entirely, and for the latest variants, they are more effective against preventing illness or serious illness than against infection (an important clinical distinction), but that's still a huge deal, and it limits spread by reducing duration of illness (infectiousness window) or virus particles produced (the degree of infectiousness).

> In short, mandates should be imposed only if science is 100% clear.

This is another way of saying that you categorically oppose all mandates. Science is never "100% clear", ever.

> They don't "acknowledge" that

> because it is not a true

> statement. Masks do limit spread

> of COVID-19.

I would love that I’m wrong. Can you please send me the link to US based study showing that masks mandates limit spread of COVID? As far as I know, californa had mask mandates while Florida did not and both states had similar number of COVID cases per capita. Florida had 6,614,806 cases while California had 10,367,437.

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