School Masking Policies and Secondary SARS-CoV-2 Transmission

Abstract

OBJECTIVES Throughout the coronavirus disease 2019 (COVID-19) pandemic, masking has been a widely used mitigation practice in kindergarten through 12th grade (K–12) school districts to limit within-school transmission. Prior studies attempting to quantify the impact of masking have assessed total cases within schools; however, the metric that more optimally defines effectiveness of mitigation practices is within-school transmission, or secondary cases. We aimed to estimate the impact of various masking practices on secondary transmission in a cohort of K–12 schools. METHODS We performed a multi-state, prospective, observational, open cohort study from 7/26/2021 to 12/13/2021. Districts reported mitigation practices and weekly infection data. Districts that were able to perform contact tracing and adjudicate primary and secondary infections were eligible for inclusion. To estimate the impact of masking on secondary transmission, we used a quasi-Poisson regression model. RESULTS 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. CONCLUSIONS Secondary transmission across the cohort was modest (<10% of total infections) and universal masking was associated with reduced secondary transmission compared to optional masking.

Association between School Mask Mandates and SARS-CoV-2 Student Infections: Evidence from a Natural Experiment of Neighboring K-12 Districts in North Dakota

“…Studies of schoolbased mask mandates are particularly prone to bias [9] as student cases detected within the school may be at least 20x more likely to have been contracted outside of school than in [10]. Other observational studies have reported a negative association between school mask mandates and SARS-CoV-2 cases [11,12,13] but may have had important methodological limitations [9,14].…”

“…While observational studies of school mask mandates have had con icting results, randomized studies have failed to detect an impact of masking on participants under 50 years of age [1][2][3][4][5][6]. Here we report the results of a natural experiment in two large K-12 school districts in Fargo, North Dakota, Fargo Public Schools (FPS) and West Fargo Public Schools (WF), to estimate the association between school mask mandates and COVID-19 infections.…”

Compliance with Barrier Gestures during COVID-19 Pandemic as a Function of the Context: A Longitudinal Observational Survey at the University of Liège

“…Moreover, the Omicron variant, which is currently predominant [ 30 ], seems to be able to escape antibodies elicited by vaccination [ 31 , 32 ]. Since the response to the vaccine depends on the variant, and given that gestures such as physical distancing, mask wearing, and handwashing have shown a certain capacity to reduce transmission [ 33 , 34 , 35 ], barrier gestures do not seem obsolete yet and can be, along with proper indoor ventilation [ 36 ], a good non-variant-specific support for vaccination, to reduce virus circulation. As non-specific means of control, they have a positive impact on the circulation of other viruses such as influenza [ 37 , 38 ], so can be used during future pandemics.…”

Face masking for children - time to reconsider

“… 8 , 9 They used a larger, nationally representative dataset over a longer period and, after replicating the original result, failed to find a significant relationship between mask mandates and case rates in the expanded sample (p=0.936) even controlling for differences across districts. 9 Other similar US observation studies reporting lower infection rates associated with mandatory masking policies, one conducted in Arizona during July-August 2021, 10 and another multistate study conducted during July-December 2021, 11 have also been faulted for methodological biases. 12 , 13 The problems with such observational studies, as discussed in detail by Chandra and Hoeg, 9 is that mask mandates are usually accompanied with other mitigations, such as stronger public health messaging, increased household and community testing, different contact tracing policies and COVID-19 vaccine requirement, which may all contribute to lower infection rates.…”