"You’ve got to be very careful if you don’t know where you are going, because you might not get there."
As cases of COVID-19 ascend in areas of the US, some schools are reverting to requiring masks. Of course this is accompanied by renewed claims that they are ineffective. In fact, Florida governor Ron DeSantis issued an executive order barring local school districts from requiring their students to wear masks, claiming that there was no evidence that masks prevent infection in schools. That claim has been levied over and over by many politicians, talking heads, pundits, and assorted Facebook “experts.” But, they are flat wrong. There are multiple lines of evidence from a variety of disciplines—including materials science, infectious diseases, pediatrics and epidemiology—showing that masks can help protect children and teachers from getting COVID in schools. Some of that evidence has already been presented in these pages, and I now add to that body of evidence, more data recently summarized in Scientific American.
- For starters, laboratory experiments show that masks block the respiratory droplets and aerosols that transmit SARS-CoV-2, the virus that causes COVID. In one test, an engineering team at the University of Wisconsin–Madison used a machine in a classroom setting to pump out particles the same size as those that carry the virus from an infected person. The researchers placed several CPR dummies with or without masks around the room and measured the degree to which the aerosols penetrated the masks. They reported that a surgical mask reduced the chances of penetration by 382 times when compared to the maskless mannequins.
- Then, in the real world, not a laboratory setting, several epidemiological studies also concluded that masks in schools work. Researchers at the ABC Science Collaborative in North Carolina collected data from more than a million K–12 students and staff members from schools across that state, which mandated masking in schools from August 2020 until July 2021. The scientists reported little in-school transmission when the mask mandates were in place during the fall, winter or summer months. During this time, in-school transmission remained low as COVID cases fluctuated outside the schools. With mask mandates, rates of within-school spread were as low as one percent.
- Masks, combined with other prevention efforts, also reduce the risk that students might bring home the virus to parents or other relatives. An online survey of 2.1 million Americans by researchers at Johns Hopkins University showed a 38 percent increased risk of COVID-related illness in households with a child attending school in person. That risk went down, however, as the number of school-based mitigation measures, including mask mandates went up.
- Studies done in wider communities beyond schools give the strongest real-world evidence that masks stop COVID’s spread. An international team of researchers conducted a randomized controlled trial involving nearly 350,000 people across 600 villages in rural Bangladesh. Half of the villages got free cloth or surgical masks and a promotional campaign encouraging their use. The other half did not. The researchers found that the mask intervention significantly curbed coronavirus transmission.
Bottom line: The effectiveness of masks in schools is supported by many different studies and analyses that show similar results. There are more than a dozen studies beyond those cited here, that all point to the same conclusion:
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