The Evolving Science of Face Masks and COVID-19

Since the Centers for Disease Control and Prevention began recommending that members of the public mask up last spring, additional research has backed the use of face masks to combat the coronavirus. While knowledge gaps still remain, experts agree that masks should be used — and increasingly, they are emphasizing the use of better masks.

In our last deep dive into the research on masks in April 2020, we explained that there were some lab studies that supported the idea that masks would be effective against the coronavirus, or SARS-CoV-2. But direct evidence that face masks prevent transmission of respiratory viruses in a community was limited.

In some ways, that basic takeaway hasn’t changed much. Benjamin Cowling, an epidemiologist at the University of Hong Kong, told us that “there is good mechanistic evidence from laboratory studies that masks should have an effect on transmission” and that “evidence from randomized trials has not been consistent with a large effect of masks on transmission, but has been consistent with a small effect of masks on transmission.”

“I continue to believe that mask use will reduce transmission, although mask use alone is not enough to prevent COVID from spreading in a community,” he said in an email.

Some experts remain skeptical that masks — at least the ones used by most people today — have much effect on transmission of SARS-CoV-2, although they still think people should wear them.