How Did Lifting School Mask Mandates Affect COVID-19 Infections?

It is an understatement to say mask mandates, intended to prevent the spread of COVID-19, have been controversial. This is especially true of masking in schools, which some have criticized as hindering students’ learning and social development.

The efficacy and adherence of children to mask mandates has also been called into question. However, by the end of February 2022, children and adolescents had a higher COVID-19 incidence rate than any other age group.

Massachusetts was 1 of 18 US states, including Washington, DC, that instated a universal masking policy across public schools during the 2021-2022 school year. In response to updated COVID-19 guidelines from the Centers for Disease Control and Prevention (CDC), Massachusetts reversed their school mask mandate on February 28, 2022.

One study, published this week in The New England Journal of Medicine, used the sudden lifting of mask mandates as a unique opportunity to research the efficacy of masks in schools at preventing COVID-19.

The investigators assessed COVID-19 incidence by length of time school districts adhered to mask mandates. They analyzed school district characteristics between districts that chose to continue versus rescind mask mandates. Finally, the study compared COVID-19 infections among students and staff in districts that lifted masking requirements to districts that sustained masking requirements.

The study included 72 public, non-charter school districts in the greater Boston, MA area, with a total of 294084 students and 46530 staffers. The study duration was the 40 calendar weeks of the 2021-2022 school year, which ended on June 15, 2022.

Using a difference-in-difference analysis for staggered policy implementation, the investigators compared COVID-19 incidence among students and staff.

Before the statewide rescinding of masking policy, COVID-19 incidence rates were similar between all school districts. In the 15 weeks after mask mandates were rescinded, there were an additional 44.9 COVID-19 infections per 1000 students and staff. This accounted for an approximate 11901 cases, 29.4% of the cases in all districts during the study period.

Interestingly, the school districts that chose to sustain mask requirements tended to have older buildings that were in worse condition. These districts that continued mask mandates averaged more students per classroom, and had higher percentages of low-income students, students with disabilities, Black or Hispanic students, and students who were English-language learners.

“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 authors wrote. They noted that universal mask mandates ensure protection for populations most at risk of COVID-19 infection due to structural racism.