The randomized trial was conducted among over 340,000 people across 600 villages
An enormous randomized research involving more than 340,000 people across 600 villages in Bangladesh has found -- some of the strongest real-world evidence yet -- that masks can help slow the spread of Covid-19.
The largest randomized study, conducted by researchers at Yale University, Stanford University, University of California and others, was able to show the effectiveness of masks -- surgical masks in particular -- in preventing coronavirus transmission in a real-world community setting, according to media reports.
Previous studies, albeit smaller, in laboratories and hospitals had shown that masks help prevent the spread of Covid-19. But the new findings demonstrate that efficacy in the real world and on an enormous scale, reports said.
"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," Laura Kwong, one of the co-authors of the study and an assistant professor of environmental health sciences at the University of California, Berkeley, told NBC.
"I think this should basically end any scientific debate about whether masks can be effective in combating Covid at the population level," Jason Abaluck, an economist at Yale who helped lead the study, said in an interview, reports The Washington Post.
He called it "a nail in the coffin" of the arguments against masks.
The preprint study was released online on Wednesday by non-profit organization Innovations for Poverty Action and is currently undergoing peer review.
The research was led by Kwong, Yale economists Ahmed Mushfiq Mobarak of Bangladesh and Abaluck, and Steve Luby and Ashley Styczynski from Stanford. The globe-spanning team also included Bangladeshi non-profit GreenVoice.
According to media reports, the team tracked 342,126 adults in Bangladesh for five months, beginning in November last year, and randomly selected villages to roll out programs to promote their use.
The programs included distributing free masks to households, providing information about their importance, and reinforcing their use in the community.
The researchers discovered that mask-wearing increased by over 30% among the roughly 178,000 people who were urged to do so and that the change in behaviour lasted for at least 10 weeks.
After the program was instituted, they found an 11.9% drop in symptomatic Covid-19 symptoms and a 9.3% reduction in symptomatic seroprevalence, which means the virus was discovered in blood testing, said the reports.
While the effect may seem small, the results offer a glimpse of just how much masks matter, said Mobarak.
"A 30% increase in mask-wearing led to a 10% drop in Covid-19, so imagine if there was a 100% increase — if everybody wore a mask and we saw a 100% change," he added.
Masks significantly reduced symptomatic infections among older adults and found that surgical masks were more effective than cloth versions, said the researchers.
The study’s findings have significant implications for countries that rely on mitigation measures to prevent the spread of the virus until vaccines become more widely available. However, there are lessons for countries like the United States, where some communities are reimposing mask mandates to combat the delta variant outbreak.
Independent experts who were asked to review the study have applauded its scope, with some speculating that it might be the most compelling evidence for mask use ever.
The research is part of an ongoing project that looks not only at the efficacy of masking, but also public health methods for encouraging mask adoption among communities.
It is now being expanded to include other villages and cities in Asia and Sub-Saharan Africa. The researchers also intend to track the effect of masks on asymptomatic transmission, said the media reports.