Failed face mask trial shows why more masks are needed - Los Angeles Times
About half of these volunteers were chosen at random to receive 50 surgical face masks and were asked to wear them whenever they left home for the next month.
The other half did not get masks and served as controls.
Overall, 95 of the 4,862 volunteers who made it to the end of the study became infected with SARS-CoV-2, the coronavirus that causes COVID-19.