Face masks considerably reduce transmission of COVID
https://www.iza.org/publications/dp/13319/face-masks-considerably-reduce-covid-19-cases-in-germany-a-synthetic-control-method-approach
"Assessing the credibility of the various estimates, we conclude that face masks reduce the daily growth rate of reported infections by around 40%."
if it is used correctly
Water will kill you if used incorrectly
