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Most people already early convinced themselves by pure logic that masks should have an impact, still today you see this opposed here&there.

Looks like a well carried out study and another data point, many influencing factors considered, data available.

Full tweet: The case for masking up: new study shows tight-fitting #FFP2 & vKN95 face masks drastically reduce the risk of #COVID19 infection - but even ill-fitting masks still significantly reduce the risk of infection https://bit.ly/31m9JKE @maxplanckpress

Their summary: https://www.mpg.de/17916867/coronavirus-masks-risk-protectio... "Well-fitting FFP2 masks reduce the risk at least into the per thousand range."

Full paper: "An upper bound on one-to-one exposure to infectious human respiratory particles" https://www.pnas.org/content/118/49/e2110117118