On the Effectiveness of Masks

City Journal has a post by Jeffrey H. Anderson that examines the actual published medical literature on the effectiveness of face masks in preventing the spread of viral infections. Here’s the TL/DR—

In sum, of the 14 RCTs {randomized controlled trials] that have tested the effectiveness of masks in preventing the transmission of respiratory viruses, three suggest, but do not provide any statistically significant evidence in intention-to-treat analysis, that masks might be useful. The other eleven suggest that masks are either useless—whether compared with no masks or because they appear not to add to good hand hygiene alone—or actually counterproductive.

That appears to be consistent with the basic physics of how filters work.

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