evidence: In other words, the research followed CDC's changing masking recommendations. But this was still an inaccurate summary of how the situation unfolded. Much of the masking research conducted throughout 2020 and into this year consisted of literature reviews and meta-analyses of studies performed during past flu seasons—that is, before April 2020—all of which concluded that the evidence was mixed and masks had limited impact on viral transmission. The problems were manifold. Epidemiological studies had no way to decouple the effects of masking from other interventions, for example. One of the clinical trials CDC cited in support of masks probably enrolled 130 people who were vaccinated against influenza and classified them as flu cases. Two other studies had no control group; another found "a 13 times higher risk of infection in the cloth mask arm" compared to medical masks. Some of the results didn't even reach statistical significance. [...] Moreover, randomized clinical trials have shown inconsistent or inconclusive results, with some studies reporting only a marginal benefit or no effect of mask use. Thus, surgical and similar masks are often considered to be ineffective. On the other hand, observational data show that regions or facilities with a higher percentage of the population wearing masks have better control of COVID-19.