A study of schools in the Boston area found that masking mandates were linked with significantly reduced numbers of Covid cases in schools.
The New York Times reports that the study found infection rates were lower among masked students — even in Boston public schools, where many buildings are old and lack good ventilation systems, classrooms are crowded, and students are more often from at-risk communities.
"Our results support universal masking as an important strategy for reducing Covid-19 incidence in schools and loss of in-person school days," the study concludes. "As such, we believe that universal masking may be especially useful for mitigating effects of structural racism in schools, including potential deepening of educational inequities."
The study, by scientists at Harvard’s T.H. Chan School of Public Health and Massachusetts General Hospital, the Boston University School of Public Health and Boston’s Public Health Commission, has been published in The New England Journal of Medicine.
Massachusetts kept masking in place in public schools at the start of the 2021-22 school year but rescinded the policy in February.
Researchers tracked state data on Covid cases week by week in 72 school districts, comparing the two that had retained masking for 15 weeks — Boston and Chelsea — with 70 others that had lifted mask requirements at different times.
Removing of mask mandates was associated with an additional 44.9 Covid cases per 1,000 students and staff members, corresponding to an estimated 11,901 cases during the 15-week period, the scientists concluded.
“We saw sustained, increased rates of Covid incidence consistently in schools that lifted the mask requirement,” said Tori L. Cowger, the study’s first author and a postdoctoral fellow at the Harvard T.H. Chan School of Public Health.
Because people who tested positive were instructed to isolate for at least five days, the additional cases led to at least 17,500 missed school days for students and 6,500 missed school days for staff members, the study calculated.