Daniel Lemire's blog

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Science and Technology links (November 28th 2020)

There is uncertainty about the effects of face masks. The low‐moderate certainty of the evidence means our confidence in the effect estimate is limited, and that the true effect may be different from the observed estimate of the effect. The pooled results of randomised trials did not show a clear reduction in respiratory viral infection with the use of medical/surgical masks during seasonal influenza. There were no clear differences between the use of medical/surgical masks compared with N95/P2 respirators in healthcare workers when used in routine care to reduce respiratory viral infection. Hand hygiene is likely to modestly reduce the burden of respiratory illness. Harms associated with physical interventions were under‐investigated.

It does not follow that you should not wear masks or that you should avoid washing your hands. I do and I recommend you do too. However, you should be critical of any statement to the effect that science is telling us that masks and hand washing stop airborne viruses, especially when such statements are made in a political context.