A huge randomized trial of communities in Bangladesh seems to provide the clearest evidence to date that wearing masks regularly can prevent the spread of the covid-19 pandemic. The study found that villages where masks were heavily promoted and became more popular experienced significantly lower rates of covid-like symptoms and confirmed past infections than villages where masks were worn. These improvements were even more pronounced for peoples with free surgical masks over cloth masks..
There is a lot of data emerged over the past year and a half to support the use of masks during the covid-19 pandemic, both in the real world and in the the laboratory. But it is less clear exactly what advantage these masks can bring to users (and their communities), and there have been at least some studies inconclusive in showing a remarkable benefit.
One problem when interpreting all this information is that we have relied heavily on observational studies, which can only show a correlation between two things, and not establish a cause-and-effect relationship. There could be other factors that explain why one city has a higher mask disguise rate and a lower rate of diagnosed cases than another city, for example, rather than helping to cause the latter.
However, late last year, dozens of scientists partnered with public health advocacy organizations and the Bangladeshi government to conduct a massive random trial of masks, often regarded as the gold standard. of the tests. And on Wednesday, them released the results of his research in a working paper through the non-profit research Innovations for Poverty Action.
The study included 600 villages in a single region of the country with more than 350,000 adult residents together. Similar villages were randomly assigned to two conditions (a pair of villages with similar population density, for example, would go to one or the other condition). In one of the conditions, researchers and their partners promoted the use of masks through various incentives between November and 2020 January 2021. These incentives included free masks, support from local leaders, and sometimes economic rewards for peoples who achieved widespread use of masks. In two-thirds of the intervention villages, the free masks delivered were surgical, while one-third received free cloth masks. In the second condition, the researchers simply observed the villages and did nothing to animate the masks during that time.
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Residents in the villages where the masks were encouraged began to wear them more, although there did not appear to be any push or incentive than the others. In the end, about 42% of the residents of these villages wore masks regularly, compared to 13% of those in the control group. And in these communities, the chances of people reporting symptoms that could have been covid or tested positive for antibodies to the virus decreased.
Overall, the average proportion of people who showed symptoms during the weeks following the promotion of the mask dropped by 11%. in these villages compared to the control group, and the average number of people with antibodies fell more than 9%. These differences were greater for people with surgical masks (12% vs. 5% to reduce symptoms) and for residents over 60 (35% to reduce infections for older residents in villages with surgical masks).
Some of these effects could do not have they come directly from capacity of masks to block the transmission of the viruss. Those who wore masks, according to the study, were also more likely to practice social distancing. This is a relevant finding, the authors point out, as some people who have defended the mandates of masks do so by claiming that masks will only make people act more carelessly. This study suggests that the opposite is true: that masks make us more, not less, aware of others.
The findings are not yet in a peer-reviewed journal, an important step in validating any research. And they have some limitations, as does any study. The study began and ended before the advent of the Delta variant, for example, a much more transmissible version of the coronavirus that spread around the world (at that time, the Alpha variant was the most common).
The study’s author, Jason Abaluck, a health and behavior economist at Yale University, told Gizmodo in an email that his team has submitted the paper for publication in the journal Science. On Twitter, Abaluck has addressed other possible warnings from the study. Some have pointed out, for example, that the authors only found a protective effect of the masks for people under 50 when experiencing covid-like symptoms, and not for having antibodies (for the elderly, a reduction was observed. of symptoms and antibodies the board in the villages wearing masks). But Abaluck he argues that this may be due simply to the fact that only 40% of people with symptoms opted for the test, so estimates from this group may be less accurate. And even if somehow the masks had no direct effect on people under 50, they can reduce the spread of the virus from younger people to older people, so masking would continue to be a net positive. at the population level.
The authors also call this masks A greater effect could be conceived when slowing the spread of the current pandemic at the population level than when the study was concluded, given the greater transmissibility of Delta per case. And because they noticed a significant effect after a modest increase in the use of masks, the benefits could be even greater with widespread masking.
“Our results should not imply that masks can only prevent 10% of covid-19 cases, let alone 10% of covid-19 mortality,” they wrote. “Our intervention induced 29 people out of every 100 to wear masks, with 42% of people wearing masks in total. The total impact with almost universal masking (perhaps achievable with alternative strategies or stricter application) can be several times higher than our 10% estimate. “
If this assumption turns out to be true, it provides more support for models that show that universal mask coverage in places like the U.S. can still significantly reduce the impact of the pandemic. A recent prediction by researchers at the University of Washington, for example, dear that universal mask coverage could prevent up to 50,000 deaths on December 1 this year.
Perhaps most importantly at the individual level, the study also suggests that fabric masks should be phased out as a recommended mask option and that surgical masks should be the default for progress, the authors say.
“While fabric masks clearly reduce symptoms, we cannot rule out that they have zero or only a small impact on symptomatic SARS-CoV-2 infections,” they wrote.