Lifting universal masking in schools – Incidence of Covid-19 among pupils and staff
Schools are an important but politically contested space in the response to Covid-19, which makes analyzes like this particularly relevant for policy makers. We estimated that the lifting of masking requirements in Greater Boston-area school districts in March 2022 contributed to 45 additional cases of Covid-19 per 1,000 students and staff over the following 15-week period. Overall, this estimate corresponded to nearly 12,000 additional Covid-19 cases among students and staff, which represented one-third of cases in school districts that lifted masking requirements during this time and most likely translated into a substantial loss of in-person school days.
We observed that the effect of school masking policies was greatest during weeks when background incidences of Covid-19 in surrounding towns and villages were highest, a finding that suggests that universal masking policies can be most effective when implemented before and throughout periods. high transmission of SARS-CoV-2. According to CDC guidance at the time, as well as updated guidance issued in August 2022, universal masking would not have been recommended until the incidences of Covid-19 in schools and surrounding communities were already approaching. their peak (May 2022); at that time, a substantial proportion of the effects of the masking policies we observed had already accrued. As such, relying on lagging measures such as CDC Covid-19 community levels and Covid-19 hospitalizations to inform school masking policies is most likely insufficient to prevent Covid-19 cases and loss. of in-person school days, and policymakers could instead consider measures of community transmission (e.g. SARS-CoV-2 sewage concentration or Covid-19 incidence) to inform these policies.
To understand the political decisions of Covid-19, attention must be paid to power and to the existing historical and socio-political contexts.10.40 Structural racism and racial capitalism operate through multiple pathways, including higher levels of household and employment overcrowding in essential industries and lower levels of access to tests, vaccines and treatments; these structural forces differentially concentrate the risk of SARS-CoV-2 exposure and severe Covid-19 in low-income and Black, Latino, and Indigenous communities.9-11.18 In our study, school districts that chose to maintain masking requirements longer tended to have school buildings in worse physical condition and more students per classroom, and these districts had higher percentages of students and personnel already made vulnerable by historical and contemporary systems of oppression (e.g., racism, capitalism, xenophobia and ableism). In Boston and Chelsea, more than 80% of students are black, Latino, or of color, and those cities were among the towns and cities in Massachusetts hardest hit by Covid-19. Students and families in these school districts have strongly advocated and organized government action to increase Covid-19 protections in schools, highlighting their role as essential workers, the risk to vulnerable family members and the consequences unequal missed work and school.41.42 The decision by some school districts to maintain school masking policies longer may therefore reflect an understanding among parents and elected officials that structural racism is embedded in public policy and that political decisions have the potential to rectify or reproduce the health inequalities.10,14,16,40
A growing body of work suggests that knowledge of differential conditions and inequitable effects may decrease support for Covid-19 protections among systematically advantaged groups, whose relative position largely insulates them from the harms of Covid-19, while increasing simultaneously building support among groups that are directly affected by systems of oppression.43-45 For example, in a randomized trial in which white people were assigned to receive information about the structural causes of persistent Covid-19 inequalities between racial or ethnic groups or not to receive such information, those who received the information were less likely to support Covid-19 prevention policies and were less likely to report individual concern about Covid-19 and empathy for groups most affected.45 In several studies and polls, black and Latino parents were more likely than white parents to support schools’ masking requirements and less likely to be confident that schools could operate safely without additional protections.43,44,46 Failing to account for the unequal baseline and continued inequitable effects of Covid-19 policies risks further exacerbating inequalities in Covid-19 incidence and educational outcomes.
Because universal masking policies in schools have been controversial, we anticipate several criticisms. One such criticism is that the benefits of universal masking in schools are outweighed by the potential disruptions to teaching, learning and social development. These effects warrant a more rigorous assessment; however, to date, there is no clear evidence that masking inhibits learning or harms development.47.48 Further, these effects could be considered alongside the range of benefits of universal masking, including fewer missed school days and staff shortages, reduced risk of illness for students and their families, and reduced economic difficulties for carers, who could be absent from work if their child is ill or if they themselves fall ill. For example, in Lexington, MA, a comparison district about 10 miles from Boston, average student and staff absences due to Covid-19 during weeks when masking was optional were 50% higher than absences during previous weeks, when masking was necessary (see Supplementary Appendix).
Additionally, severe Covid-19 and post-Covid conditions remain significant risks in school-aged children. Like much of the United States, the greater Boston area has low Covid-19 vaccination coverage among children (only 53% of children ages 5-11 had been fully vaccinated in Boston and Chelsea through October 2022, compared to 67% in comparison districts), with substantial inequalities according to race or ethnic group and socio-economic status. Additionally, we observed greater benefits from maintaining masking among staff, a finding that underscores that universal masking is an important part of comprehensive workplace protections for staff, who may be at higher risk of contracting a severe form of Covid-19 than students. Additionally, staff absences may be particularly significant for students who require additional educational supports and services, including ELL students and students with disabilities.
A second common criticism is that there are alternative approaches to reducing transmission and severe disease, such as improved ventilation and increased vaccination coverage. Our results show that the better ventilation and higher vaccination coverage in school districts that lifted masking requirements than in districts that maintained masking requirements were insufficient to prevent all cases of Covid-19 in those schools. Therefore, while we cannot weigh the full range of individual and societal implications of masking policies, our study highlights the important role of interim universal school masking policies in mitigating the effects of Covid-19, while longer-term and more sustainable policies are developed to increase uptake of vaccination and improve learning environments.
One of the main strengths of this study is our use of difference-in-difference methods with staggered dates of the lifting of masking requirements. Although some factors related to exposure to SARS-CoV-2 differ between school districts, difference-in-differences methods yield robust analyzes in the context of confounders that do not change with the time (for example, socio-demographic characteristics or the condition of buildings) or do not coincide with the change in the policy of interest. In sensitivity analyses, the benefits of masking requirements persisted after controlling for community-level indicators of Covid-19, vaccination coverage and past incidence of infection. Additionally, we found that school districts that lifted masking requirements were districts that might have been expected to have a lower incidence of Covid-19 (on average, they had buildings in better physical condition and had higher vaccination coverage), suggesting that any residual confounding by Covid-19 risk would have led to the harms of lifting masking requirements being underestimated overall.
A limitation of this study is that we did not have data regarding Covid-19 testing in individual school districts. However, DESE ended the practice of mandatory testing only for unmasked close contacts in January 2022, and data from this “test and stay” program shows that too few schools have continued the program for it to be able to. explain our results. Under the most extreme assumptions, additional testing of unmasked close contacts could explain less than 7% of estimated excess cases. Overall, our results should be interpreted as the effect of universal masking policies and not the effect of masking per se, since masks were still encouraged in most school settings. Despite this consideration, the effect of lifting masking requirements has been substantial.
The winter wave of the B.1.1.529 (omicron) variant in the 2021-2022 school year will not be the last wave of Covid-19 to affect students and staff, and ongoing efforts to cope to the inequitable environmental risks and effects of Covid-19 in school settings are urgently needed. Our results confirm that universal masking with high-quality masks or respirators during periods of high community transmission is an important strategy to minimize the spread of SARS-CoV-2 and the loss of in-person school days. Our results also suggest that universal masking may be an important tool to mitigate the effects of structural racism in schools, including the differential risk of severe Covid-19, educational disruption, and the health and economic effects of transmission. secondary to household members. School districts could use these results to develop equitable mitigation plans in anticipation of a possible winter surge of Covid-19 in the 2022-2023 school year, as well as clear decision thresholds for removing masks at school. as the wave decreases.