March 9, 2022 -- School mask mandates helped to protect children and teachers from the coronavirus last fall, according to a new study released by the CDC.
Public school districts in Arkansas with mask requirements had 23% lower rates of the coronavirus among students and staff than districts without mandates from August to October 2021 as the Delta variant spread.
The CDC has faced criticism in the past for overstating the benefits of masking at schools based on previous studies, according to The New York Times. Some studies have found that mask mandates work in schools, while others have found that mask requirements don’t lower the rates of the coronavirus in children.
But the latest CDC research appears to have avoided the study design problems noted in other studies and has supported the evidence for using masks to protect children, the newspaper reported.
“It passes the smell test,” Louise-Anne McNutt, PhD, a former CDC researcher and now an epidemiologist at the State University of New York at Albany, told the newspaper.
“The estimates of the impact of masks are consistent with other studies that show masks have a modest, but important, reduction of SARS-CoV-2 transmission,” she said.
The research team compared the rates of COVID-19 cases at 233 public school districts in Arkansas between Aug. 23 and Oct. 16. About a third had full mask mandates, a fifth required masks in certain settings or groups, and half had no mask requirements. They also looked at COVID-19 rates in the surrounding community, social and economic status, and staff and student vaccination rates.
During the study period, statewide COVID-19 community transmission levels declined from substantial to moderate, and vaccination coverage increased. Average weekly district-level case rates among students and staff were consistently higher than community case rates and decreased over time from 745 cases per 100,000 people in late August and early September to 137 cases per 100,000 people in mid-October. During the same time, vaccination coverage increased from 13.5% to 18.6% among staff and older students.
The research team found that districts with full mask mandates had lower COVID-19 rates, relative to the case rates in the surrounding community, than districts without mandates. Overall, districts with full mask requirements had 23% lower COVID-19 rates, compared with districts with no requirements, including 24% lower among staff and 23% lower among students. The researchers also found that partial masking policies didn’t help as much as full mask mandates.
Among 26 districts that switched from a no-mask policy to a full or partial requirement during the study period, case rates dropped more than would have been expected based on community cases at the time, the study authors wrote. A week after a mask policy was put in place, case rates among students and staff decreased significantly.
“In areas with high COVID-19 community levels, masks are an important part of a multicomponent prevention strategy in K-12 settings,” the study authors wrote.
The study still had several limitations. Since it was done from August to October, researchers aren’t sure whether the same results held once the Omicron variant became the dominant form of the coronavirus at the end of the year.
What’s more, the study couldn’t account for other prevention efforts at schools, such as quarantine rules, classroom ventilation, and whether people followed physical distancing guidelines. Future studies could match nearby schools in the same community that had different masking policies to study their effects, Jason Abaluck, PhD, a behavioral and health economics professor at the Yale University School of Management who led a study on masking in Bangladesh, told the Times.
“Figuring out how severe an outbreak has to be to warrant mask mandates in schools requires making best guesses about the costs, which remain highly uncertain given existing evidence,” he said.
Those costs could include discomfort, Abaluck noted, as well as difficulties in communicating at school. At the same time, the study marks an improvement on previous research, he said.
“This study and the broader literature on masking suggests that in places where hospitalization and deaths are very high, the benefits of mask wearing in schools may be considerable,” he said.