Shawn Vestal: Time and time again, researchers link mask use with lower rates of infection

About one year ago, schools in North Carolina opened for in-person instruction. Some followed a program of strict pandemic protocols – strict mask wearing, distancing and hand-washing – and some did not.

A team of Duke University researchers tracked infections in the mask-wearing schools, compared them to community spread at the time, and found “extremely limited” secondary transmission in the 11 school districts that followed the protocols, even as case rates were high in the surrounding community.

During a nine-week study period, researchers tested and found 773 students and staffers were infected in the community and spent time in schools; only 32 secondary cases resulted within the schools, and most of those were associated with instances in which mask wearing had not been followed.

“Our cohort study revealed that enforcing SARS-CoV-2 mitigation policies, such as mask-wearing, physical distancing, and hand hygiene, resulted in minimal clusters of SARS-CoV-2 infection and low rates of secondary transmission in schools,” the authors concluded.

It’s called “Incidence and Secondary Transmission of SARS-CoV-2 Infections in Schools,” and it was published in the journal Pediatrics in April. Read it yourself: pediatrics.aappublications.org/content/147/4/e2020048090.

So, there’s one. Here’s another: The Centers for Disease Control and Prevention tested students in 20 elementary schools in a Salt Lake City school district that returned to in-person learning last August in a community where viral spread was high.

They identified 51 students and staff who brought infections into 48 separate classrooms; even with only 3-foot distancing, a strict adherence to masking apparently helped keep the “secondary attack rate” very low – just five secondary infections, none in the same school.

“These results suggest that when 6-foot distancing is not feasible, schools in high-incidence communities can still limit in-school transmission by consistently using masks and implementing other important mitigation strategies,” the CDC concluded in this study.

You can read it yourself at www.cdc.gov/mmwr/volumes/ 70/wr/mm7012e3.htm.

Another: Researchers conducted a two-week study last December in elementary schools in Springfield and St. Louis County, Missouri, when in-school classes had resumed while community spread was high. They found almost no secondary infections from 37 infected individuals who were identified as having been in the schools – another association between masking and infection rates in schools falling far below those in the community.

“Schools implementing strategies including mask mandates, physical distancing, and increased ventilation had much lower SARS-CoV-2 transmission than in the community,” the authors said.

Read it yourself: www.cdc.gov/mmwr/volumes/70/wr/mm7012e4.htm.

And another: the CDC evaluated rates of in-school infection in Florida, which opened to in-person learning last year, with some schools masking and some schools not: “Higher rates among students were observed in smaller districts, districts without mandatory mask-use policies, and districts with a lower proportion of students participating in remote learning,” the authors of the paper, published in March, concluded.

Read it yourself: www.cdc.gov/mmwr/volumes/70/wr/mm7012e2.htm?s_cid=mm7012e2_w.

These studies show a clear association between mask-wearing, along with other prophylactic measures, and much lower rates of viral spread in schools. They show correlations, which we know can be misinterpreted, and each has limitations, which they list meticulously. They are not randomized controlled trials, which would likely be impossible and unethical during a pandemic, and each finding is each suggestive, not conclusive.

That’s why it’s important to rely on large bodies of evidence, not single studies, and on findings that are reproduced. So it’s reassuring to know that studies in Chicago, Wisconsin, Missouri, Italy, Switzerland and Germany produced the same results.

As classes begin in Spokane, and as the small, hot flame of mask fury burns on, it’s important to know that the best of our scientific knowledge – real knowledge, as gathered and evaluated by serious people – tells a simple, consistent story: Masks help prevent infection.

And not just in schools. A CDC evaluation of outbreaks last year among 382 service members aboard the USS Theodore Roosevelt found that those who wore masks regularly showed a 70% reduced risk of infection. (www.cdc.gov/mmwr/volumes/69/wr/mm6923e4.htm)

In Missouri last year, two infected hair stylists worked with 139 clients while wearing face coverings. Sixty-seven customers were tested, and none was infected. Separate studies in Beijing households and on American airplanes show strong correlations between mask use and reduced secondary infections.

In addition, there is mounting evidence of effectiveness on a communitywide scale.

“At least 10 studies have confirmed the benefit of universal masking in community level analyses: in a unified hospital system, a German city, two U.S. states, a panel of 15 U.S. states and Washington, D.C., as well as both Canada and the U.S. nationally,” the CDC wrote in an evaluation of the state of mask science. “Each analysis demonstrated that, following directives from organizational and political leadership for universal masking, new infections fell significantly.”

There’s that and much more to peruse at the CDC’s roundup of mask science: www.cdc.gov/coronavirus/2019-ncov/science/science-briefs/masking-science-sars-cov2.html.

There’s a lot of research about masks, and it tells the same story. We’re still learning and our knowledge will grow, but at this point it adds up to a strong endorsement of the effectiveness of masking.

Maybe the people telling you otherwise are just unfamiliar with it.