Universal Masking in School Works. New Data Shows How Well

In many schools across the U.S.—consistent with trends across the country—the only masks that have been seen recently were those on Halloween costumes. Mask requirements generally went by the wayside in the spring of 2022, when the first Omicron wave subsided and the CDC modified its recommendations around masking, replacing universal masking with masking triggered by high case and hospitalization rates. Since that time, even when masking has been recommended by the CDC given a high Community Levels category, schools and other indoor facilities have rarely reinstated the requirement. Sustaining kids’ health and learning is foremost on parents’ and educators’ minds. But clearly a persistent central question has been the simple one: Do universal school masking requirements actually work?

A new study in the New England Journal of Medicine sheds some light on this question. The authors examined COVID-19 case rates in districts in the Boston area after the Massachusetts Department of Elementary and Secondary Education (DESE) lifted statewide school masking requirements in February 2022, in accordance with CDC guidance. What followed was a natural experiment in the impact of mask requirements, as school districts removed the requirement at different points in time or not at all. Two school districts (Boston and nearby Chelsea) retained the requirement throughout the study period.

The authors found that COVID-19 rates were similar among districts before the mask requirement was rescinded, then diverged quickly, with higher case rates in districts immediately following the removal of the mask requirement. Approximately 12,000 cases, or 30% of all cases during the study period, were attributable to rescinding the mask requirement. The resulting illnesses led to substantial loss of in-person school days— an estimated minimum of 17,500 days of school absence in students and 6,500 days of staff absence—arguing for masks as a critical component of optimizing learning.

An important insight from the study was that school districts that maintained required masking more often had school buildings in poor condition, crowded classrooms, and a higher proportion of individuals more vulnerable to harmful health outcomes, including those with disabilities, than the more affluent districts that lifted mask requirements. All else being equal, the risk of SARS-CoV-2 transmission is higher in buildings with inadequate ventilation and filtration and with more people in smaller spaces, so the need for protective measures such as masks is greater in lower-resourced schools. The importance of this protection was further heightened because other mitigation measures were also dropped at the same time, including contact tracing, physical distancing, COVID testing, and quarantining for close contacts.

Wealthier communities may feel they can unmask more readily because of lower transmission risk and because of higher vaccination rates. The study suggests that this perception is incorrect, as cases increased substantially among schools that lifted mask requirements, despite the fact that many of these were better-resourced schools structurally more prepared to avoid and mitigate disease. While the study does not capture the broader contributions to community transmission, excess cases tend to place a disproportionate burden on the health and financial wellness of less affluent community members. Therefore, allowing wealthier communities to drive the decision making around mask requirements is not only a manifestation of inequity, but threatens to widen it.

Remedying the injustice requires giving lower-resourced schools a central voice in policy decision making and making tangible and immediate investments in those schools to make them safer. Beyond investing in the schools themselves, which will have multiple benefits for learning and wellness beyond COVID-19, additional measures to protect students, staff, and their families include sick leave and other structural supports that help increase vaccination and booster rates and equitable access to health care.

Broadly, there are some who will quickly dismiss the new study’s findings, arguing that masks don’t work to reduce SARS-CoV-2 transmission. The evidence is clear on this point. Masks can block and filter the aerosols that carry SARS-CoV-2, and better masks work better; this study supports previous evidence that mask policies in communities prevent transmission, providing data specifically on policies in the school setting. While there are challenges for schools, including mask compliance, the lack of N95s designed for young kids, and necessary mask removal at lunchtime, there are many high-quality masks (such as KF94 or KN95) that work well for kids and are extremely comfortable. The study by Cowger and colleagues does not have information on the types of masks worn across the Boston area, but multiple school districts communicated about the importance of higher-quality masks to combat more transmissible variants, and made these masks freely available to students.

So, what should we do with the new information provided by this study? As a school nurse, an environmental health researcher, and an emergency medicine physician, we find this information compelling and important to act on. Right now, pediatric practices and hospitals are overrun with COVID-19, RSV, flu, and many other respiratory viruses, and the winter and holiday season (when things typically get much worse) is just around the corner. Student and staff absenteeism are on the rise early in this school year, the fourth academic year impacted by COVID, but the first one with no protective measures employed on a consistent basis. The off-ramps were clear once universal masking ended; it’s the on-ramps that are not accessible or equitable.

Although “mild” disease has provided the rationale for low concern about COVID among children, sheer numbers in a winter surge will mean increased burden on the health care system and many more cases of serious sequelae, such as long COVID, among children. Now is the time for schools to develop specific plans for illness mitigation. Short-term mask requirements, based on clear metrics and targets, and with the provision of high-quality masks to families, can make a big difference. That will keep kids and staff in school and parents at work.

Strategic use of masks should be referred to as a primary means of increasing learning—not the opposite—because kids cannot learn when they are at home sick, in the hospital, or when their instructors are out sick. Any strategy should also include appropriate accommodations, including routine masking regardless of CDC Community Level, for students at high risk for severe COVID-19 due to immunocompromising or other conditions. This approach can be used broadly by any organization that wishes to improve worker protection, play a role in limiting community transmission, and ensure that public spaces are accessible to all.

The new study by Cowger and colleagues reinforces that we have the tools to protect both our students’ health and their learning. Now is the time to actually use them, but are the decision-makers in schools and in local, state, and federal government paying attention?