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Comment by mike_hearn | Hacker News Reader

Next sentence: "It would be accurate to say that the review examined whether interventions to promote mask wearing help to slow the spread of respiratory viruses, and that the results were inconclusive."

... which is what I just said: some people got mad at them because their review found no reliable evidence that masking worked (or rather, that mask mandates worked, but these are virtually the same thing).

The null hypothesis for any medical intervention is that it has no effect. You start from that and then try to prove your hypothesis that it does have an effect, which is what medical studies are for. If you can't prove something works then we fall back to the null and assume it doesn't. So that isn't a misleading or inaccurate interpretation of the results, though it would certainly have been politically convenient for the Cochrane organization if their reviewers could have supported the claims of public health authorities.

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That sentence doesn't say what you think it says. It says "interventions to promote mask wearing". That's not mask wearing, it's telling people to wear masks. It is both true that wearing masks helps and that it's hard to tell if promoting mask-wearing changed enough behavior to matter. Mostly, those interventions do nothing.

That's an ambiguous sentence. The main results of the study conclude:

Wearing masks in the community probably makes little or no difference to the outcome of influenza‐like illness (ILI)/COVID‐19 like illness compared to not wearing masks (risk ratio (RR) 0.95, 95% confidence interval (CI) 0.84 to 1.09; 9 trials, 276,917 participants; moderate‐certainty evidence.

Which I think is definitive.

The original Plain Language Summary for this review stated that 'We are uncertain whether wearing masks or N95/P2 respirators helps to slow the spread of respiratory viruses based on the studies we assessed.' This wording was open to misinterpretation, for which we apologize.

> no reliable evidence that masking worked(or rather, that mask mandates worked, but these are virtually the same thing).

No it's not the same thing, and that's the key point. If you tell people that masking doesn't work (which is false) then of course mask mandates won't work because adherence will be low. A self-fulfilling prophecy really.

Compliance for COVID mask mandates was measured and found to be extremely high, especially at the start (>95%). These mandates were enforced by harsh penalties so high compliance levels is no surprise. Thus you can't argue mask mandates didn't work because of low compliance.

Also health authorities told people masks were highly effective. That's what justified the mandates. So you can't argue mask mandates didn't work because people were told it wouldn't work.

Therefore there's no self fulfilling prophecy here. It didn't even matter what individuals thought anyway, we all had to wear masks.

Although Cochrane much prefers to use RCTs, people have run regressions over the data and there was no link between levels of mask wearing and infection rates. It sucks but it appears that masks just can't stop aerosolized virus, which spreads like a gas. They aren't designed to do that so it's no knock against the manufacturers, who in some cases explicitly warned people that their products would be useless for that purpose (https://pbs.twimg.com/media/EfNmzptXkAEg9Od?format=jpg&name=...).

> ... which is what I just said: some people got mad at them because their review found no reliable evidence that masking worked (or rather, that mask mandates worked, but these are virtually the same thing).

This is not virtually the same thing. Comparing those two is wildly disingenuous and you know it.

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