Study demonstrates face mask effectiveness against COVID-19


SAN FRANCISCO, Calif. (KRON) – A recent study done by Stanford, Yale and UC Berkeley confirms that mask-wearing is an effective way to decrease the transmission of COVID-19.

In this largest mask study yet, researchers found that masks reduced COVID-19 cases by 9% and surgical masks prevented 35% of symptomatic infections among those 60 years and older.

Many of us often wonder which masks are most effective, especially now with the delta variant. 

While some people may perceive these surgical masks as flimsy or non-reusable, researchers found that these surgical masks are more effective than cloth ones, even after you wash and reuse them.

Researchers at Stanford, Yale, and UC Berkeley found just how effective masks can be in reducing the spread of COVID-19 in the largest mask study to date.

Their recent study was done in Bangladesh across 600 villages and more than 350,000 adults.

While they found masks in general provided a 9% reduction in COVID-19 cases, surgical masks were more effective and reduced cases by 11%. Researchers say effectiveness continued to climb among older adults.

“In people who were 60 and above we found that we were able to prevent 35% of COVID-19 cases,” Ashley Stycynski said. 

Infectious disease expert at Stanford University, Ashley Stycynski who was one of the lead authors of this research says the study was done when cases were lower before the delta variant became the dominant strain, so they predict case reduction would be larger today.

“We think this is probably an underestimate of the real estimate of the impact of masks for a number of reasons, including the fact that we only measured COVID-19 among people who reported symptoms consistent with COVID-19 definitions during the study period so we might have missed cases that were asymptomatic,” Stycynski said. 

Stycynski says these lessons can be applied to the United States, especially when comparing surgical masks and cloth masks, even after several washes.

“One of the barriers we had at the time to rolling out surgical masks that people would perceive them to be flimsy or less durable and so they wanted something that they could re-use so we responded by doing the test on what happens if you wash a surgical mask and what we found was that that filtration efficiency drops from about 95% to about 70-75% after that first wash but then it stays there after subsequent washes still giving you more protection than your cloth masks,” Stycynski said. 

In comparison, Stycynski says cloth masks only offer about 10 to 20% filtration efficiency.

She says mask-use also tripled among people when providing free masks, informing people about the importance of covering their mouth and nose, reminding people when they were unmasked in public, and by showing that community leaders or prominent figures were also wearing their masks.

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