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The results of a massive study in Bangladesh unequivocally show that surgical masks reduce the spread of SARS-CoV-2, scientists say.
The results – of the highest-quality type of benchmark clinical trial known as a randomized controlled trial – are expected to “end any scientific debate” about the effectiveness of masks in fighting the spread of COVID – 19, Jason Abaluck, an economist at Yale and one of the authors who helped lead the study, said The Washington Post.
“This is an incredibly difficult but important study to do,” Megan Ranney, an emergency physician and professor at Brown University who was not part of the study, told The Post. “The anti-masks keep saying, ‘Where is the randomized controlled trial?’ Well, there it is.”
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For the past year and a half, scientists have claimed that the masks have reduced the spread of the virus. But it is very difficult to study how well masks help curb transmission in the real world, where not everyone is masking, using the same quality of masks, or even wearing masks correctly.
Observational studies, which simply compare mask-wearing behaviors with infection rates in different areas, can be clouded by so many other factors. Randomized trials – in which people are randomly assigned whether or not to receive a medical intervention – are the strongest form of evidence. But these are expensive and difficult to drive, especially for behavior like masking.
In the new study, researchers from Bangladesh and the United States tested the effectiveness of the promotion and use of masks in 600 villages in Bangladesh. The study, which involved more than 342,000 adults, is the largest randomized trial ever to use masks, according to the Post.
The study was published as preprint on the nonprofit website Innovations for Poverty Action on Sept. 1 as it is peer reviewed for publication in the journal Science, according to the Post.
In the trial, which ran from November 2020 to April 2021, around 178,000 people benefited from the “intervention” and around 164,000 people did not. Everyone in the intervention group received free masks, received extensive information about the importance of wearing the mask, had community leaders as role models and received in-person reminders for eight weeks, according to the study.
People in the control group did not receive any of these interventions. The researchers then placed observers throughout the community who tracked, on a weekly basis, how many people were correctly wearing masks and physically distancing themselves in mosques, markets and main entry roads to villages and stalls. tea.
Five and nine weeks after the trials began, the researchers asked participants about symptoms like COVID-19. Then, about 10 to 12 weeks after starting the trial, they took blood samples from symptomatic participants and tested them for anti-SARS-CoV-2 antibodies.
Masking interventions tripled appropriate mask use from 13.3% in the control group observations to 42.3% in the masking intervention group. They also found that physical distance was around 24.1% in the control group observations, compared to 29.2% in the treatment group. Five months after the trial, “the impact of the intervention wore off,” meaning fewer people wore masks correctly, but mask wear remained 10% higher in the intervention group compared to the control group, the researchers wrote.
In the intervention group, 7.62% of people had COVID-19-like symptoms, compared to 8.62% in the control group. The researchers collected blood samples from nearly 11,000 participants and found that the intervention reduced symptomatic COVID-19 infection by 9.3%.
“Our results should not be interpreted as implying that masks can only prevent 10% of COVID-19 cases, let alone 10% of COVID-19-related mortality,” the authors wrote in the article. This is because the intervention only led to 29 more people out of 100 to wear masks. “The total impact with near universal masking – perhaps achievable with alternative strategies or stricter enforcement – may be several times greater than our estimate of 10%,” they wrote.
The villages received either fabric masks or surgical masks. In villages that received surgical masks, symptomatic infection was reduced by 11.2% compared to the control group. This percentage was even higher among the elderly: among those who were 60 years of age or older and who received free surgical masks along with the other procedures, symptomatic infection was reduced by 34.7% compared to the control group. They did not find that cloth masks reduced symptomatic infection compared to control groups.
The study is one of many that show the benefits of masking, but it has some limitations.
For example, although they were told to keep a low profile and wear simple clothing, researchers who asked participants how they wore masks and physically distanced themselves may have been recognized by study participants, who then may have changed their behaviors, the authors wrote. The study also couldn’t explain whether the masks made symptoms less severe by lowering the viral load people were exposed to, or whether they reduced new infections completely.
Originally posted on Live Science.
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