2 ms·

There have been a number of laboratory studies performed that show varying levels of effectiveness for different kinds of masks and materials (where "effectiven

by timr 5y ago

There have been a number of laboratory studies performed that show varying levels of effectiveness for different kinds of masks and materials (where "effectiveness" is defined in all sorts of different ways that may or may not be relevant). Prior to Covid-19, there was a low-quality evidence base that didn't provide much signal either way: https://www.cebm.net/covid-19/masking-lack-of-evidence-with-politics/ https://www.cebm.net/covid-19/masking-lack-of-evidence-with-... Strapping a mask on a mannequin or to a nozzle is, of course, very different than asking people to wear them everywhere. For evidence of real-world effectiveness of a medical intervention, you do a controlled trial. We could have done some, but we did not. It is notable -- but not at all perfect -- that the only RCT conducted with masks and Covid-19 in 2020 found no significant personal protective effect: https://www.acpjournals.org/doi/10.7326/M20-6817 https://www.acpjournals.org/doi/10.7326/M20-6817 It is a well-done study, and certainly limits the claims that can be made for masks, but doesn't answer every question. A good cluster RCT might have been able to address the question of whether or not masks protect others, for example.

mike529 5y ago
This good cluster RCT is in the midst of being done. https://www.nber.org/papers/w28734 https://www.nber.org/papers/w28734 In this paper they demonstrated an intervention in Bangladesh that increased mask usage by 30 percentage points (from ~10% to ~40%). In the follow-up paper they are doing random antibody testing between the two groups.
Izkata 5y ago
It probably won't be as satisfying for you, but in the US mask-wearing got split along political lines. You can compare red areas (haven't worn masks for months to a year) to blue areas (were still mostly wearing them up to this month when the CDC guidelines changed). Overall, no noticeable effect.
- bluGill 5y ago
  There are confounders though that make such data not useful (I'm not sure how much statistics can find data in the noise or not though - but it won't be trivial). Red areas are in general more rural and spread out, while blue areas are denser population. Thus blue areas are naturally a different risk level. Also masks and political stance are not a perfect correlation. I personally know democrats who don't wears masks and republicans who do.

by timr 5y ago

mike529 5y ago

This good cluster RCT is in the midst of being done. https://www.nber.org/papers/w28734 https://www.nber.org/papers/w28734 In this paper they demonstrated an intervention in Bangladesh that increased mask usage by 30 percentage points (from ~10% to ~40%). In the follow-up paper they are doing random antibody testing between the two groups.

Izkata 5y ago

It probably won't be as satisfying for you, but in the US mask-wearing got split along political lines. You can compare red areas (haven't worn masks for months to a year) to blue areas (were still mostly wearing them up to this month when the CDC guidelines changed). Overall, no noticeable effect.

bluGill 5y ago
There are confounders though that make such data not useful (I'm not sure how much statistics can find data in the noise or not though - but it won't be trivial). Red areas are in general more rural and spread out, while blue areas are denser population. Thus blue areas are naturally a different risk level. Also masks and political stance are not a perfect correlation. I personally know democrats who don't wears masks and republicans who do.