[sanxiyn]

Mask's effect size on seroprevalence is probably zero. So no effect is expected result.

That's because mask acts on R0, not seroprevalence. After acting on R0, if R0 is >1, exponential growth, if <1, exponential decay. So no effect, unless it is the thing that pushes one from >1 to <1.

[lotu]

Also, they aren't testing masking effect on seroprevalence (or R0), they are testing the effect of sending out free masks and encouraging masking. That is only going to move the percent of people masking up or down a few percent at best.

[sampo]

The study says:

> The intervention increased proper mask-wearing from 13.3% in control villages (N=806,547 observations) to 42.3% in treatment villages (N=797,715 observations)

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