Largest study of masks yet details their importance in fighting Covid-19

A study involving more than 340,000 people in Bangladesh offers some of the strongest real-world evidence yet that mask use can help communities slow the spread of Covid-19.

The research, conducted across 600 villages in rural Bangladesh, is the largest randomized trial to demonstrate the effectiveness of surgical masks, in particular, to curb transmission of the coronavirus. Though previous, smaller studies in laboratories and hospitals have shown that masks can help prevent the spread of Covid, the new findings demonstrate that efficacy in the real world — and on an enormous scale.

“This is really solid data that combines the control of a lab study with real-life actions of people in the world to see if we can get people to wear masks, and if the masks work,” said Laura Kwong, an assistant professor of environmental health sciences at the University of California, Berkeley, and one of the co-authors of the study.

The preprint study was posted online Wednesday by the nonprofit organization Innovations for Poverty Action and is currently undergoing peer review.

“A 30-percent increase in mask-wearing led to a 10 percent drop in Covid, so imagine if there was a 100-percent increase — if everybody wore a mask and we saw a 100-percent change,” he said.

The scientists said masks significantly reduced symptomatic infections among older adults, and found that surgical masks were more effective than cloth versions.