The researchers recruited more than 6,000 volunteers from around the country who spent at least three hours each day with people from other households and didn’t wear masks for their jobs. About half of these volunteers were chosen at random to receive 50 surgical 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. That’s an infection rate of just under 2%.
But no matter how the researchers sliced and diced their data, they could not find a strong signal that the volunteers in the mask group were more protected than their counterparts in the control group.
In a typical clinical trial, this is the point where researchers would say their intervention didn’t work. But in this case, the investigators went the other way.
The problem, they said, wasn’t with the masks. The problem was that people didn’t use masks enough.