The authors of a study based on a massive randomized research project in Bangladesh say their results provide the best evidence that widespread use of surgical masks may limit the spread of coronavirus by the communities.
The pre-published article, which screened more than 340,000 adults across 600 rural villages in Bangladesh, is by far the largest randomized study of HIV. effectiveness of masks to limit the spread of coronavirus infections.
Its authors say the study offers real and conclusive evidence for what laboratory work and other research has strongly suggested: use of masks can have a significant impact in limiting the spread of symptomatic covid-19, the disease caused by the virus.
“I think, basically, this could end any scientific debate about whether or not masks are effective in combating covid at the population level,” Jason Abaluck, a Yale economist who helped lead the study, said in an interview, calling it “a nail in the coffin” of arguments against masks.
The researchers estimate that among a group of Bangladeshi adults in the study who were encouraged to wear masks, use rose 28.8% after the intervention. When screened, the group had a 9.3% reduction in the seroprevalence of symptomatic covid-19, meaning that the virus was confirmed by blood testing, plus an 11.9% reduction in covid-19 symptoms.
The study’s authors – led by the following lead researchers Abaluck, Laura Kwong, Steve Luby, Ahmed Mushfiq Mobarak and Ashley Styczynski – a global team that includes researchers from Yale, Stanford and Green Voice, a non-profit organization, emphasized that this it does not mean that the masks were only 9.3% effective.
“I think it would be a big mistake to read this study and say, ‘Oh, masks only prevent 10% of symptomatic infections,'” Abaluck said. “The number would likely be many times higher if mask use were universal,” he said.
The study is being peer reviewed in the journal. science. The authors allowed journalists early access to the results because of their potential importance in public health debates.
Independent experts invited to examine the research praised its scale; some have suggested it might be the most convincing argument so far for wearing masks.
“This study is incredibly challenging but very important to carry out,” said Megan Ranney, an emergency room physician and professor at Brown University who was not involved in the research. “Anti-mask people keep saying, ‘Where’s the randomized controlled trial?’ Well, it’s here.”
“It’s not just about modeling or going back to school,” said Lawrence Gostin, director of the O’Neill Institute for National and Global Health Law at Georgetown University, who was also not involved. “This is the epitome of scientific knowledge.”
The research is part of an ongoing project led by Abaluck and his co-authors that focuses not only on the mask’s effectiveness, but also on public health methods to encourage the adoption of masks in communities.
The team chose Bangladesh because its co-author and Yale economist, Mobarak, was from there and had worked there before, and because of the growing funding options.
The sheer scale of the project, which started in November and ended in April 2021, is remarkable. About 178,000 Bangladeshi residents were in an intervention group and were encouraged to wear masks. An additional 163,000 people were in a control group, in which no intervention was made.
The project assessed levels of mask-wearing and social distance through direct observations by an undercover team in the community, mosques, markets and other meeting points.
“This is a project that cannot be handled by a few people,” said Abaluck. “That’s why there are hundreds of people involved in the project. That’s why the article has… I don’t even know how many co-authors. Dozens of co-authors.”
The use of masks became mandatory in Bangladesh from March 2020, although adoption has been restricted. The researchers found they were able to increase mask use in the intervention group from 13% to 42% – an increase of 28.8%. The result was observed and shown to be consistent for ten weeks and continued after the interventions stopped.
The group attributed a “cocktail” of four interventions to substantially increasing the use of masks in the community: providing free masks door-to-door; provide information about the benefits of masks, reinforce the use of masks, and endorse the use of masks by trusted local leaders.
“It’s a precise combination of things and a set of tasks that need to be done concurrently and integrated,” Mobarak told Yale Insights in May.
When these behavioral findings were released earlier this year, they received a positive response from experts. But discoveries about the effectiveness of the masks are likely to have a far greater impact.
“I see no reason why the interaction between the mask and the virus should be any different in rural Bangladesh or rural Kansas or urban New York or San Francisco,” Gostin said. “The biology is the same.”
The study contains a trio of key observations, Ranney said: First, it offers even more evidence that masks work to protect the individual and the community. Because the research group was only able to document cases in which people were symptomatic and HIV-positive for the virus, Ranney agreed that the results may be underestimated.
“For me this is the minimal effect of wearing masks on a community,” she said. “I expected the actual effect of the masks to be much greater, considering the limitations they had in scaling covid in this study.”
Second, it indicates that higher quality masks offer greater protection. And third, the study shows how to motivate people in a community to wear masks, making masks a social norm.
Gostin said the research also brushed aside the “pernicious” idea that masks were for personal protection only. “(The use of masks) works as a blanket that we have to adopt for the general population,” he said.
The study doesn’t want to be the last word on the masks. The authors found that while tissue masks clearly reduce symptoms, they “cannot reject” the idea that, unlike surgical masks, they are likely to protect very little from symptomatic coronavirus infections, or possibly not at all.
Abaluck emphasized, however, that the research has not produced evidence that fabric masks are ineffective.
The results “do not necessarily show that surgical masks are much, much better than tissue masks, but we found much clearer evidence of the effectiveness of surgical masks,” he said.
Abaluck also noted that the intervention group practiced more social detachment, which could complicate the findings about the masks. However, he noted that in places such as mosques, where many attendees held their services, there was no “social distance” and indoor environments were not very ventilated – but there was greater use of masks.
The authors plan to conduct further research, including an assessment of how masks limit symptomatic spread – either by lowering viral load so fewer people have symptoms or by preventing infections entirely.
But existing research can have a significant impact on future policy – and it can also raise questions about past policy.
In this survey, “people were given masks and told they were expected to use them,” Ranney said. Something similar almost happened in the United States. In April 2020, during the Trump administration, the Post planned to send five masks to every American home. But the strategy was abandoned.
“One of the things I keep thinking about… If we had all been given masks the same way,” as participants in this study did, Ranney said, “would we have lowered the Covid death rate?” / Translation by Lívia Bueloni Gonçalves