Table 3.

Summary of Evidence of Impact of Masking in School Settings

Study/Country	Setting	Study Type	Mask Intervention	Simultaneous Interventions	Results	Data Source
Falk et al. [40], USA	17 K-12 in-person schools, Wisconsin	Cohort, investigated COVID-19 cases and compliance with mask use, Aug 31–Nov 29, 2020	Masking required for students & staff	Students in cohorts	Reported rate of student mask wearing was >92%. Case rates among students & staff (191 cases among 5530 persons or 3453/100K) were lower than in the county overall (5466/100K). 1 in 20 cases among students linked to in-school transmission. No infections among staff were school acquired.	Wood County COVID-19 dashboard, weekly surveys to calculate school masking compliance
Stein-Zaimer et al. [106], Israel	Israel Regional Public High School, grades 7–12	Outbreak investigation	On May 19–21, 2020, during an extreme heatwave, the Ministry of Health exempted pupils from wearing masks. Windows were closed with 35–38 students per class.		10 days later, a major outbreak occurred, with student attack rate 13% vs staff 17%.	Israel Ministry of Health
Panovska-Griffiths et al. [107], UK (preprint)	UK secondary schools (ages ≥12 y)	Modeling study, simulated mask effective coverage in schools & community settings, estimated as the product of the mask efficacy (per-contact risk reduction) and coverage (proportion of contacts in which they are worn)	Mandatory masking in secondary schools (re-opened Sept 1). Mandatory masking in community started Jul 24, 2020.		Assuming current test-and-trace isolate levels, adoption of masks in secondary schools in addition to community settings will reduce size of a second wave as compared with no adoption of masks. Greater benefit of mandatory masks in secondary schools if effective coverage of masks is high (30%) under current testing and tracing levels.	UK COVID-19 dashboard, NHS Test and Trace

Society guidance: Centers for Disease Control and Prevention [108]: masks recommended when students are <6 feet apart and should be considered when students are >6 feet apart. Wearing masks may not be possible for younger students and those with mental/physical health conditions. World Health Organization [109]: masks recommended for children >5 years. Apply a risk-based approach for children 6–11 years. Children ≥12 years should follow WHO guidance for adult mask use. American Academy of Pediatrics [22]: strongly recommends universal use of masks for children ≥2 years.

Abbreviations: COVID-19, coronavirus disease 2019; NHS, National Health Service; WHO, World Health Organization.