Widespread use of coronavirus face masks can help control virus transmission: study

In the ongoing debate about coronavirus face mask effectiveness, a new study published this week suggests that widespread use of face masks can help to prevent large outbreaks of COVID-19. 

The study, published Tuesday in The Lancet Digital Health, surveyed more than 300,000 Americans 13 years of age or older about their mask-wearing habits. Participants were asked questions like how likely they were to wear a face mask while in public places, such as while shopping for groceries, or visiting family and friends who do not live in their household. 

Of those who responded, some 85% said they were "very likely" to wear a mask while grocery shopping, and roughly 40% said the same about visiting family and friends. Overall, those 65 or older were more likely to report wearing a mask, as were Black and Hispanic Americans and those who reported living in a large urban area. 

By the end, a logistic model "controlling for physical distancing, population demographics and other variables found that a 10% increase in self-reported mask-wearing was associated with an increased odds of transmission control," the researchers, from Boston Children’s Hospital, wrote. 

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In other words, the researchers found that just a 10% increase in face-mask wearing by those within a certain zip code tripled the odds that the community could keep control of virus transmission, or tripling the community’s chances of keeping the coronavirus reproduction number (R0) below one. 

An R0 is a mathematical term that is related to how infectious a disease is, or the average number of people who will contract the illness from a single person who is infected with it. An R0 below one indicates that a disease "will decline and eventually die out," per Healthline.

While the study authors identified certain limitations – they didn't account for contact tracing and testing, for example, and participants were asked to self-report their mask-wearing habits – they ultimately concluded that "communities with high reported mask-wearing and physical distancing had the highest predicted probability of transmission control."

"The widespread reported use of face masks combined with physical distancing increases the odds of SARS-CoV-2 transmission control. Self-reported mask-wearing increased separately from government mask mandates, suggesting that supplemental public health interventions are needed to maximize adoption and help to curb the ongoing epidemic." 

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"The evidence is clear: masks work," Dr. Hannah Clapham of the National University of Singapore said in an article accompanying the study. 

However, she noted, "their use is a non-targeted control measure, wherein the whole population is involved, rather than just known or suspected cases."

Or, in other words, "buy-in from society as a whole is, therefore, necessary for the success of the intervention," she wrote.