One problem with "look at the epidemiology" as an approach is that the virus is such a moving target. I'm citing these figures from memory, so apologies if I ma

One problem with "look at the epidemiology" as an approach is that the virus is such a moving target. I'm citing these figures from memory, so apologies if I mangle them, but with OG covid you could mask up properly and spend an hour in an enclosed space with viral particles in the air and have a low risk of infection, while with omicron you had maybe five minutes masked the same way before you'd catch an infectious dose. More generally, the trouble with evaluating masking is all the confounders. I spent the early pandemic in Japan, where ubiquitous masking was a highly effective barrier to spread. One reason it may have worked as well as it did is that people talked less with the masks on. But there were already strong social norms against talking in confined public places, and the public health authority stressed airborne spread. How much did that contribute? I feel like the mask issue is irretrievably lost at this point in the US, but it's important to stress that in places like Japan and Taiwan it worked quite well, at least until omicron got so infective that even stringent adherence was no longer adequate. But there's no way to untangle it from the changes in social behavior that accompanied it, some of them a physical result of the masks (less talking), some due to social signaling aspects of mask wearing, and many unrelated.