Have you looked ?Direct Evidence of the Efficacy of Public Mask Wearing
If there is strong direct evidence, either a suitably powered randomized controlled trial (RCT), or a suitably powered metaanalysis of RCTs, or a systematic review of unbiased observational studies that finds compelling evidence, then that would be sufficient for evaluating the efficacy of public mask wearing, at least in the contexts studied. Therefore, we start this review looking at these types of evidence.
https://www.pnas.org/content/118/4/e2014564118
