Face masks for Covid pass their largest test yet
nature.com
nature.com
The study found an effect size of zero in the cloth mask cohort, and an 11% difference in the surgical mask cohort. Effect sizes that managed significance were just barely significant, at a p-value of 0.043. Also, the researchers didn't do any baseline serology, so it's quite difficult to know if there was a starting bias influencing the final results. It's also difficult to know the degree to which the non-blinded nature of the study and voluntary seroprevalence testing biased the outcome. At such small effect sizes, questions like these matter a great deal.
Nevertheless, it is encouraging that someone actually bothered to do a proper RCT of masking as "protection for others", and this study has several points that should be widely communicated (e.g. the ineffectiveness of cloth masks). However, I would not say that "masks passed their test" is really one of them...these results are pretty mediocre.
Vinay Prasad of UCSF has made an excellent summary of the results of the Bangladesh RCT, and I recommend it strongly:
These are not the surgical/procedure masks that we see people commonly wearing in the US.
Not only that, but they cost thirteen cents apiece.
Why don’t we have those in the US?
Edit: it’s not a very good trial, because mask compliance was poor in spite of their efforts, and they didn’t separate the mask wearing groups when evaluating the outcomes, though they could have.
I would have expected better results from the “surgical” masks.
You really have to read the original paper to assess this trial properly.
> The study’s authors found that surgical masks — but not cloth masks — reduced transmission of SARS-CoV-2 in villages where the research team distributed face masks and promoted their use.
West coast city: 90% of the people I see around wear useless cloth masks. Borders on criminal that we pretend the mask-as-virtue-statement circus we are currently undergoing has any benefit other than reduced oxygen flow.
Oxygen is smaller and easier to pass the filters than COVID-19 particles. It's possible not to have reduced oxygen flow but protect against the virus, but physically impossible to do the reverse as you suggest.
For fun, I just googled 'N95 reduced oxygen flow' and found this pearl from Stanford as the top result: https://digitalmedic.stanford.edu/myth/myth-face-masks-can-r...
> Myth: Face masks can reduce oxygen getting to the lungs and bloodstream
> ... Some masks mean you have to put more effort into breathing if you wear them for a long time.
> ... If worn for many hours without a break, an N95 mask might potentially affect oxygen levels but likely not to a dangerous extent, especially in people who are healthy.
'put more effort into breathing' aka 'suffocating at normal breath patterns'. Oh, and it actually does reduce the oxygen levels, but rest assured citizen, it is nothing to worry about. It's just a myth. There is a word I'm looking for here, miss, misty, aha, misinformation.
Personally, I don't consider that reduced airflow relevant to me or anyone I know. The people with reduced lung capacity do complain about having trouble after 15 minutes, but continue to wear them. In fact, people with reduced lung function are the most aggressive mask wearers I know.
Now consider that kids are forced to wear cloth masks all day long, day after day after day. This is a choice, there are places in the world where they are just as serious about covid as US, and yet kids can stay in class without masks.
It's a rough tradeoff. I wish we could have an adult conversation, not pretend there are no minuses and masks are a no brainer in all situations. We have replaced conversation with Twitter sloganeering.
An example: https://nltimes.nl/2021/08/23/school-year-starts-north-nethe...
> In secondary education, teachers and pupils who have been fully vaccinated for at least two weeks won't have to quarantine after contact with someone who has the coronavirus. Only unvaccinated teachers and -students need to take a self-test twice a week. Teachers and students need to maintain social distancing, and face masks are mandatory in corridors and canteens.
> In primary education, adults like teachers and parents must keep 1.5 meters apart. But for the kids, no restrictions apply other than the general rules like washing your hands regularly and staying home if you have symptoms.
Why on earth wouldn't I? My O2 levels don't seem to be too degraded by a mask. And, even if they were, I would never expect to be hired by people who saw me put them at risk. I'm not sure I would feel comfortable accepting a job from people who would hire someone who wasn't willing to wear a mask.
> I wish we could have an adult conversation, not pretend there are no minuses and masks are a no brainer in all situations.
I've never experienced a negative from wearing a mask. Some people are really opposed by I just don't get it. It makes as much sense to me as people not wearing a seat belt because they worry about chaffing.
> there are places in the world where they are just as serious about covid as US, and yet kids can stay in class without masks.
Every state that lets kids run around without masks produces news stories about COVID spreading like wildfire through the schools. I don't know why I would consider that acceptable. Kids should not be forced to get COVID for no reason.
I'm telling you the conclusions of the paper. Your faith in masks is an entirely separate question that is clearly unaffected by the data here, because it requires proving a negative.
Is it possible that cloth masks actually work, and this huge study failed to find any significant effect? Anything is possible, but the results here are indistinguishable from noise, and don't support the claim. And with every RCT that gets published showing negligible effect from community masking, the probability that the claim is true gets smaller.
Edit: Fundamentally I have an issue with any definition of risk that bounds the measure to a short time frame. For all we know the mask intervention may slow the spread speed by a small factor, but were we to measure over a year (or even longer) we might observe the same total number of infections: the virus is going to infect everyone susceptible, only at a slightly slower pace.
2. Only a portion of the people were even wearing masks. A few people wore masks and the risk of infection dropped by a few percent. Declaring masks don't work because a couple people wore them yet the entire population didn't see a complete decline in infection is illogical and dishonest.
3. The study not being able to conclude in a statistically significant way that cloth masks prevent infection is completely different from concluding that cloth masks are worthless. Your aversion to masks is completely a reflection of your bias and not supported by this study.
...there were 54,000 people in the cloth mask villages, and 106,000 people in the surgical mask villages. Compliance was over 40%.
That's more than "a few people".
[1] Airborne transmission of respiratory viruses https://www.science.org/lookup/doi/10.1126/science.abd9149
[2] Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks https://pubs.acs.org/doi/10.1021/acsnano.0c03252#
Then why are Nature reporting on them in such conclusive language?
If there is any Russian speaker around, would be instructive to take one of the old top Soviet science publications and translate the TOC.
> Then why are Nature reporting on them in such conclusive language?
Given Nature has very well-regarded peer reviewers, it seems likely that this is an earlier report on something they expect to publish as peer reviewed. Why report it now? Because people are dying and this could help them.
Are they arguing over comma locations? Waiting until the next publication date? Who knows.