not pointing to N numbers is untestable, though. To the best of my knowledge, nobody has run a "do you know how to wear a fucking mask" study. This one ain't it. Even the study's authors are unequivocal: WEAR A FUCKING MASK.
For roughly half the 600 villages, we intervened by promoting mask usage: We gave every family in each village at least three masks — one per adult, cloth or surgical — and distributed masks in public spaces, including markets. We enlisted eminent local figures to explain why wearing masks can help slow viral transmission — providing imams with scripts to be read during religious services, for instance. Local leaders also modeled proper mask-wearing. We then sent observers into public spaces to note any changes in behavior.
So while Vinay Prasad can go "are we wearing the wrong masks" from a study that wasn't about type of mask, three of the actual authors of the study are up in the WaPo going
Our research suggests that if we could get even a quarter more people wearing high-quality masks across Latin America, Africa and Asia, we could change the trajectory of the pandemic. Indeed, the reductions in infections we observed in Bangladesh with surgical masks, if extrapolated to the entire country over the past four months, could have saved nearly 25,000 lives.
Our study showed conclusively that masks are a cost-effective way to reduce infections and demonstrated that a mask-promotion strategy can work. But our broader campaign to spread the word about our approach made clear that building large-scale coalitions across NGOs and governments is essential to converting that information into programs that reach millions.
Until the vaccine supply increases — and possibly afterward — mask-wearing will remain essential worldwide. We all need to think hard about the best ways to marshal resources and apply the findings of this study to specific national and local contexts.