BANGLADESH (NewsNation Now) — Wearing a mask, especially a surgical mask, reduces the risk of symptomatic COVID-19 infection among people, according to a new large-scale study.

The study, conducted by researchers from Innovations for Poverty Action, University of California Berkley, Stanford and Yale, found that surgical masks prevented symptomatic infections among those 60 years old and older by 35%.

Mask-wearing overall reduced COVID-19 cases by 9% as well, according to the research.

Over 300,000 Bangladeshi adults participated in the study from 600 villages and more urban areas. It was conducted between November 2020 and April 2021 with some villages receiving direct access to masks and community outreach to encourage face coverings.

Bangladesh was chosen according to Stanford in part because “mask promotion is considered vital in countries where physical distancing can be difficult” in a country

“The reduction in symptomatic cases is impressive, particularly when you consider that this was a community setting, not a lab, and less than half of people who received the intervention were wearing masks,” said Dr. Ashley Styczynski, a co-author on the study and an infectious disease fellow at Stanford’s Division of Infectious Diseases & Geographic Medicine, in a news release announcing the findings.

The program used to encourage mask-wearing among residents is called “N.O.R.M.” It involved offering no-cost masks, offering information on proper mask wearing, reinforcing that in public by making it a social norm and having trusted leaders model the behavior.

The “N.O.R.M.” model increased mask wearing by 29% which researchers say was critical for reducing COVID-19 infections.

This study is the largest real-world test of masks’ effectiveness, according to researchers. They believe it can be effective in preventing infections all across the world.

The Centers for Disease Control and Prevention cites several lab studies showing masks are effective at reducing COVID-19 infections.

“These results suggest that we could prevent unnecessary death and disease if we got people to wear high-performance masks, such as surgical masks, in schools, workplaces, shopping centers, places of worship, and other indoor spaces,” said co-author Laura Kwong, an assistant professor of environmental health sciences at UC Berkeley’s School of Public Health.