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A great real test of the world of facial masks in Bangladesh shows that masks work to reduce the community spread of COVID-19. It also shows that surgical masks are more effective than fabric covers.
The study, published before the peer review, demonstrates the power of careful research and offers a wealth of lessons on the use of masks that will be important around the world. A key finding of the study, for example, is that wearing a mask does not lead people to abandon social distancing, which public health officials feared could happen if the masks gave people a false sense of security.
“What we were really able to achieve is to demonstrate that the masks are effective against COVID-19, even under a rigorous and systematic evaluation that was done in the midst of the pandemic period,” said Ashley Styczynski, MD, who was a infectious disease scholarship. at Stanford University when he collaborated on the study with other Stanford colleagues, Yale, and Innovations for Poverty Action (IPA), a large nonprofit research and policy organization currently working in 22 countries.
“And so I think people who have been holding on to masks because [they] we felt there wasn’t enough evidence, hopefully that will help them bridge that gap, ”he said.
It included more than 600 unions (or local government districts in Bangladesh) and approximately 340,000 people.
Half of the districts were given cloth or surgical face masks along with continuous reminders to wear them properly; the other half was followed up without any intervention. Blood tests of people who developed symptoms during the study verified their infections.
Compared to non-masking peoples, those wearing masks of any kind had approximately 9% fewer symptomatic cases of COVID-19. The finding was statistically significant and is unlikely to have occurred by chance.
“Someone might read this study and say,‘ Okay, you reduced COVID-19 by 9%. Great thing. ”And to which I would respond would be that, in any case, we believe this is a substantial underestimation,” Styczynski said.
One of the reasons they believe they underestimated the effectiveness of masks is that they only tested people who had symptoms, so they lost people who only had very mild or asymptomatic infections.
Another reason is that among people who had symptoms, only a third agreed to undergo a blood test. The effect may have been greater if participation had been universal.
Local transmission may also have played an important role. COVID-19 rates in Bangladesh were relatively low during the study. Most infections were caused by variant B.1.1.7 or Alpha.
Since then, Delta has taken over. Delta is believed to be more transmissible and some studies have suggested that people infected with Delta shed more viral particles. Masks can be more effective when more viruses are circulating.
The researchers also found significant differences by age and by type of mask. Villages where surgical masks were worn had 11% fewer cases of COVID-19 than towns where masks were not worn. In the villages where cloth masks were worn, on the other hand, infections were only reduced by 5%.
Fabric masks were important. Each had three layers: two layers of fabric with an outer layer of polypropylene. When testing, the filtration efficiency of the fabric masks was only 37%, compared to 95% of the three-layer surgical masks, which were also made of polypropylene.
Masks were more effective for the elderly. People aged 50 to 60 who wore surgical masks were 23% less likely to test positive for COVID compared to their peers who did not. For people over 60, the risk reduction was greater: 35%.
Rigorous research
The study was conducted over a period of eight weeks in each district. The interventions were developed in waves, the first starting in November 2020 and the last in January 2021.
The researchers handed out free cloth or surgical face masks to each home and showed families a video on the proper use of masks with promotional messages from the prime minister, an imam of the chief and a national cricket star. They also handed out free masks.
Previous studies have shown that people are not always truthful about wearing masks in public. In Kenya, for example, 88% of people who responded to a telephone survey said they wore masks regularly, but researchers determined that only 10% did.
Researchers at the Bangladesh studio not only asked people if they wore masks, but they parked in public markets, mosques, tea stalls and on roads that were the main entrances to villages and took notes.
They also tried various ways to educate people and remind them to wear masks. They found that four factors were effective in promoting the use of masks and gave them an acronym: NORM.
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N, for free masks;
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Or, to provide information through video and local leaders;
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R, for periodic reminders to people by researchers who are in public markets and offer masks or encourage anyone who does not wear any of them or who wears them correctly;
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M, for modeling, in which local leaders, like imams, wear masks and remind their followers to wear them.
These four measures tripled the wearing of masks in the intervention communities, going from a baseline level of 13% to 42%. People continued to wear the masks properly for about two weeks after completing the study, indicating that they had become accustomed to wearing them.
Styczynski said nothing else (no text message reminders, no signs posted in public places, no local incentives) moved the needle with the mask.
Lives and money saved
The study found that the strategy was also cost-effective. Giving masks to a large population and getting people to use them costs about $ 10,000 a lifetime saved from COVID, at the same time as the deployment of mosquito nets to save people from malaria, Styczynski said.
“I think what we’ve been able to demonstrate is that this is a really important tool that needs to be used globally, especially because countries have delays in accessing and deploying vaccines,” he said.
Styczynski said masks will continue to be important even in countries like the United States, where vaccines do not stop transmission 100% and there is still a large part of the population that is not vaccinated, such as children.
“If we want to reduce COVID-19 here, it’s very important that we consider the continued usefulness of masks, in addition to vaccines, and that we don’t really think about them or one or the other,” he said.
The study was funded by a grant from GiveWell.org. The funder had no role in the design, interpretation, or decision to publish the study.
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