For immediate release: February 15, 2022
Boston, MA – Before lifting mask mandates in elementary schools in the United States, local COVID-19 case rates should be well below current rates to avoid the risk of increased transmission among students, staff and families, according to a study by researchers from Harvard TH Chan School of Public Health and Massachusetts General Hospital (MGH).
Their work has been published in line on February 14, 2022, in JAMA Network Open.
“It’s critical that communities have a conversation about their goals for school mitigation,” said Andrea Ciaranello, MD, researcher in the Department of Infectious Diseases at MGH and lead author of the paper. “Do they want to prevent all transmissions at school? Or do they want to keep the number of cases among students, staff and families low enough that no one is likely to be hospitalized? Or do they want to minimize absences due to isolation and quarantine so students can enjoy in-person learning, a goal that also requires keeping overall cases low? These are all valid goals, and once they are clearly articulated, we can use a systematic mathematical approach to estimate the level of mitigation needed to achieve them.
About 37 million students attend elementary school in the United States, according to the National Center for Education Statistics, and there is little information to help school policymakers know when to lift mask mandates and when to reinstate them, though. necessary. Researchers used model-based simulations to quantify how changes in mitigation measures like masking could impact COVID-19 transmission among students, teachers, staff, and their families. The results indicated that the appropriate “exit ramps” for lifting mitigation measures and “on-ramps” for implementing mitigation measures vary considerably depending on the goals that school decision-makers want to achieve, but that for achieve a range of reasonable targets, local case rates will generally need to be well below those seen in the current wave of the pandemic before they unmask.
For example, in an elementary school where 25% of students and 70% of teachers are vaccinated, the study found that policymakers should only remove masks when the local COVID-19 case rate is below 14 cases per year. 100,000 per day, if the goal is to limit the number of additional cases to less than 10 per month. If vaccination coverage increased to 90% among students and teachers, policymakers could remove masks when the local case rate was above 50 cases per 100,000 per day and still achieve the same goal.
The study authors found that several factors could alter these case rate thresholds. In general, increasing vaccination rates or instituting weekly screening would allow schools to remove masks even when community transmission rates are higher.
Although the study focused on the Delta variant, the lead author John Giardina noted that the decision framework will still be useful for school decision-makers dealing with other variants.
“This study underscores the importance of schools setting clear goals about what they want to achieve from their policies around masks and other mitigations,” said Giardina, a doctoral student in health policy at the Center for Health Decision Sciences at Harvard Chan School. “Having data-driven metrics on when we want to remove masks or re-add them can help clarify the decision-making process and ensure that policy decisions align with both a community’s goals and respond to the ever-changing dynamics of this pandemic.
The authors were supported by the Centers for Disease Control and Prevention through the Council of State and Territorial Epidemiologists (NU38OT000297-02), the National Institute of Allergy and Infectious Diseases (R37AI058736-16S1; K01AI141576; and K08127908), the National Institute on Drug Abuse (3R37DA01561217S1) and Facebook (unlimited gift).
“Estimated model association between simulated US elementary school-related SARS-CoV-2 transmission, mitigation interventions, and vaccination coverage across local incidence levels”, John Giardina, Alyssa Bilinski, Meagan C. Fitzpatrick, Emily A. Kendall, Benjamin P. Linas, Joshua Salomon, and Andrea L. Ciaranello, JAMA Network Open, February 14, 2022, doi: 10.1001/jamanetworkopen.2021.47827
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Harvard TH Chan School of Public Health brings together dedicated experts from many disciplines to educate new generations of global health leaders and generate powerful ideas that improve the lives and health of people everywhere. As a community of leading scientists, educators and students, we work together to bring innovative ideas from the lab to people’s lives, not only achieving scientific breakthroughs, but also working to change the individual behaviors, public policies and health care practices. Each year, more than 400 Harvard Chan School faculty members teach more than 1,000 full-time students from around the world and train thousands more through online and executive education courses. Founded in 1913 as the Harvard-MIT School of Health Officers, the school is recognized as America’s oldest professional public health training program.