Surgical masks protect against COVID-199 Sep 2021 03:21
https://www.nature.com/articles/d41586-021-02457-y
"Critics of mask mandates have cited the lack of relevant randomized clinical trials, which assign participants at random to either a control group or an intervention group. But the latest finding is based on a randomized trial involving nearly 350,000 people across rural Bangladesh. The study’s authors found that surgical masks — but not cloth masks — reduced transmission of SARS-CoV-2 in villages where the research team distributed face masks and promoted their use."
"“This really should be the end of the debate,” says Ashley Styczynski, an infectious-disease researcher at Stanford University in California and a co-author of the preprint describing the trial. "
"Masks will remain an especially crucial line of defence in Bangladesh and other low- and middle-income countries, where access to vaccines is limited to non-existent. “If this changes the discourse in the US, where masks are being unnecessarily politicized, then that’s a bonus,” says Mobarak."