Gizmodo: “An enormous randomized trial of communities in Bangladesh seems to provide the clearest evidence yet that regular mask-wearing can impede the spread of the covid-19 pandemic. The study found that villages where masks were highly promoted and became more popular experienced noticeably lower rates of covid-like symptoms and confirmed past infections than villages where mask-wearing remained low. These improvements were even more pronounced for villages given free surgical masks over cloth masks. Plenty of data has emerged over the last year and a half to support the use of masks during the covid-19 pandemic, both in the real world and in the lab. But it’s less clear exactly how much of a benefit these masks can provide wearers (and their communities), and there are at least some studies that have been inconclusive in showing a noticeable benefit. One problem in interpreting all this information is that we’ve largely relied on observational studies, which can only ever show a correlation between any two things, not establish a cause-and-effect relationship. There might be other factors that both explain why one city has a higher rate of mask-wearing and a lower rate of diagnosed cases than another city, for instance, rather than the former helping cause the latter. Last late year, however, dozens of scientists teamed up with public health advocacy organizations and the Bangladesh government to conduct a massive randomized trial of masks—often seen as the gold standard of evidence. And on Wednesday, they released the results of their research in a working paper through the research nonprofit Innovations for Poverty Action…”