School Masking Policies and Secondary SARS-CoV-2 Transmission | Pediatrics

Abstract: 1,112,899 students and 157,069 staff attended 61 K–12 districts across 9 states that met inclusion criteria. The districts reported 40,601 primary and 3,085 secondary infections. Six districts had optional masking policies, 9 had partial masking policies, and 46 had universal masking. Districts that optionally masked throughout the study period had 3.6 times the rate of secondary transmission as universally masked districts.

For every 100 community-acquired cases, universally masked districts had 7.3 predicted secondary infections, while optionally masked districts had 26.4.

Secondary transmission across the cohort was modest (<10% of total infections) and universal masking was associated with reduced secondary transmission compared to optional masking.