{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,26]],"date-time":"2026-08-26T17:42:49Z","timestamp":1787766169490,"version":"build-2784847793"},"reference-count":17,"publisher":"American Academy of Pediatrics (AAP)","issue":"6","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2022,6,1]]},"abstract":"<jats:sec><jats:title>OBJECTIVES<\/jats:title><jats:p>Throughout the COVID-19 pandemic, masking has been a widely used mitigation practice in kindergarten through 12th grade (K\u201312) 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 estimated the impact of various masking practices on secondary transmission in a cohort of K\u201312 schools.<\/jats:p><\/jats:sec><jats:sec><jats:title>METHODS<\/jats:title><jats:p>We performed a multistate, prospective, observational, open cohort study from July 26, 2021 to December 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.<\/jats:p><\/jats:sec><jats:sec><jats:title>RESULTS<\/jats:title><jats:p>A total of 1 112 899 students and 157\u2009069 staff attended 61 K\u201312 districts across 9 states that met inclusion criteria. The districts reported 40\u2009601 primary and 3085 secondary infections. Six districts had optional masking policies, 9 had partial masking policies, and 46 had universal masking. In unadjusted analysis, districts that optionally masked throughout the study period had 3.6 times the rate of secondary transmission as universally masked districts; and for every 100 community-acquired cases, universally masked districts had 7.3 predicted secondary infections, whereas optionally masked districts had 26.4.<\/jats:p><\/jats:sec><jats:sec><jats:title>CONCLUSIONS<\/jats:title><jats:p>Secondary transmission across the cohort was modest (&amp;lt;10% of total infections) and universal masking was associated with reduced secondary transmission compared with optional masking.<\/jats:p><\/jats:sec>","DOI":"10.1542\/peds.2022-056687","type":"journal-article","created":{"date-parts":[[2022,3,9]],"date-time":"2022-03-09T04:38:56Z","timestamp":1646800736000},"source":"Crossref","is-referenced-by-count":43,"title":["School Masking Policies and Secondary SARS-CoV-2 Transmission"],"prefix":"10.1542","volume":"149","author":[{"given":"Angelique E.","family":"Boutzoukas","sequence":"first","affiliation":[{"name":"aDuke Clinical Research Institute"},{"name":"bDepartments of Pediatrics"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kanecia O.","family":"Zimmerman","sequence":"additional","affiliation":[{"name":"aDuke Clinical Research Institute"},{"name":"bDepartments of Pediatrics"},{"name":"cCo-Chair, The ABC Science Collaborative, Durham, North Carolina"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Moira","family":"Inkelas","sequence":"additional","affiliation":[{"name":"dFielding School of Public Health"},{"name":"eClinical and Translational Science Institute, University of California Los Angeles, Los Angeles, California"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"M. 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