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by incrudible 1668 days ago
The (to my knowledge) largest study on community transmission finds ~10% reduction:

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

There are many other studies that find no or modest reduction. We need to accept lower results as an upper bound to effectiveness, especially when it comes to how the average person uses masks, versus how a health care professional.
1 comments
chimprich 1668 days ago
I had a quick scan of that paper and read

"The results in all specifications are the same: we estimate a roughly 9% decline in symptomatic seroprevalence in the treatment group (adjusted prevalence ratio (aPR) = 0.91 [0.82, 1.00]) for a 29 percentage point increase in mask wearing over 8 weeks."

So when mask use increased 29%, symptom prevalence reduced by 9%? That doesn't seem quite the same argument as the one you're making.

> We need to accept lower results as an upper bound to effectiveness

Why?

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incrudible 1668 days ago
> So when mask use increased 29%, symptom prevalence reduced by 9%? That doesn't seem quite the same argument as the one you're making.

It is a real word example. It's not an increase of 29%, it's an absolute difference of 29%. Specifically, mask wearing in the intervention villages was 42%, in the control 13%. That is, in a hypothetical village where mask wearing approaches 100%, you might expect something like a 20-30% reduction, assuming a linear correlation. Again, that's not the real world.

> Why?

If an intervention is effective, the effect needs to reproduce. If it doesn't, the larger effect likely occurred by chance. Publication bias promotes positive results and inhibits negative or null results.

You have the same problem with all these COVID drugs. Remdesivir appeared to have an effect in early trials, now it's proven useless. Molnupiravir was initially report to be 50% effective, now it's down to 30%. At the other end of the aisle, you see that Ivermectin has many small studies showing remarkable effectiveness, but the larger ones show little to no effect.

If you apply scientific standards, you must apply them across the board. You must not let wishful thinking guide your decisions.

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