key: cord-0799452-9oejm9sc
authors: Jehn, Megan; McCullough, J. Mac; Dale, Ariella P.; Gue, Matthew; Eller, Brian; Cullen, Theresa; Scott, Sarah E.
title: Association Between K–12 School Mask Policies and School-Associated COVID-19 Outbreaks — Maricopa and Pima Counties, Arizona, July–August 2021
date: 2021-10-01
journal: MMWR Morb Mortal Wkly Rep
DOI: 10.15585/mmwr.mm7039e1
sha: 893cc91f9c57c0595835f27c6977954309c0b79c
doc_id: 799452
cord_uid: 9oejm9sc

CDC recommends universal indoor masking by students, staff members, faculty, and visitors in kindergarten through grade 12 (K-12) schools, regardless of vaccination status, to reduce transmission of SARS-CoV-2, the virus that causes COVID-19 (1). Schools in Maricopa and Pima Counties, which account for >75% of Arizona's population (2), resumed in-person learning for the 2021-22 academic year during late July through early August 2021. In mid-July, county-wide 7-day case rates were 161 and 105 per 100,000 persons in Maricopa and Pima Counties, respectively, and 47.6% of Maricopa County residents and 59.2% of Pima County residents had received at least 1 dose of a COVID-19 vaccine. School districts in both counties implemented variable mask policies at the start of the 2021-22 academic year (Table). The association between school mask policies and school-associated COVID-19 outbreaks in K-12 public noncharter schools open for in-person learning in Maricopa and Pima Counties during July 15-August 31, 2021, was evaluated.

location, grade levels present, † † enrollment, and Title I status § § (a measure of a school population's socioeconomic status) were obtained from the Arizona Department of Education. Crude and adjusted logistic regression analyses with 95% confidence intervals (CIs) were performed in Stata (version 15; StataCorp) and adjusted for school county, enrollment size, grade levels present, Title I status, and 7-day COVID-19 case rate in the school's zip code during the week school commenced. Schools with late mask requirements were excluded from these analyses because of their mixed exposure status during the sampling time frame (e.g., schools might have enacted mask requirements after an outbreak). Vaccination coverage for staff members and students was not available at the school level.

Data were available for 1,020 of 1,041 (98.0%) K-12 public noncharter schools in Maricopa and Pima counties. Twenty-one (2.0%) schools had outbreaks reported <7 days after school began and were excluded from the analyses. Among the 999 (96.0%) schools included in the analysis, 210 (21.0%) had an early mask requirement, 309 (30.9%) had a late mask requirement enacted a median of 15 days after school started (interquartile range = 9-17 days), and 480 (48.0%) had no mask requirement (Table) . During July 15-August 31, 2021, 191 school-associated outbreaks occurred, 16 (8.4%) in schools with early mask requirements, 62 (32.5%) in schools with late mask requirements, and 113 (59.2%) in schools without a mask requirement.

In the crude analysis, the odds of a school-associated COVID-19 outbreak in schools with no mask requirement were 3.7 times higher than those in schools with an early mask requirement (odds ratio [OR] = 3.7; 95% CI = 2.2-6.5). After adjusting for potential described confounders, the odds of a school-associated COVID-19 outbreak in schools without a mask requirement were 3.5 times higher than those in schools with an early mask requirement (OR = 3.5; 95% CI = 1.8-6.9).

CDC recommends universal indoor masking in K-12 schools (1); however, masking requirements in K-12 schools vary by school district, county, and state. In the two largest Arizona counties, with variable K-12 school masking policies at the onset of the 2021-22 academic year, the odds of a school-associated COVID-19 outbreak were 3.5 times higher in schools with no mask requirement than in those with a mask requirement implemented at the time school started. Lapses in universal masking contribute to COVID-19 † † The variable for grade levels present was included within the model as three separate indicator variables, corresponding to elementary, middle, and high school. § § https://www2.ed.gov/programs/titleiparta/index.html Abbreviations: K-12 = kindergarten through grade 12; NC = not calculated. * Chi-square and Fisher's exact tests were used to calculate p-values between schools with early mask requirements (mask requirement in place at the start of the school year) and those with no mask requirements, which are included in logistic regression analyses. Schools with late mask requirements instituted mask requirements at any time after the start of the school year. † During July 15-August 31, 2021. § Defined as the presence or absence of grades taught at the school. Categories are not mutually exclusive, and p-value was not calculated. Three separate indicator variables were used to capture presence of these grade levels in the multivariate model. ¶ Calculated as all new confirmed and probable COVID-19 cases per 100,000 population occurring in each zip code containing a school included in this analysis during the surveillance week in which the school' s academic year started. Categories presented are based on CDC community transmission metrics, included as a continuous variable in the multivariate model. ** Under Title I, financial assistance is provided to local educational agencies and schools with high numbers or high percentages of students from low-income families. outbreaks in school settings (3); CDC K-12 school guidance recommends multiple prevention strategies. Given the high transmissibility of the SARS-CoV-2 B.1.617.2 (Delta) variant, universal masking, in addition to vaccination of all eligible students, staff members, and faculty and implementation of other prevention measures, remains essential to COVID-19 prevention in K-12 settings (1).

COVID-19: guidance for COVID-19 prevention in K-12 schools

Outbreak associated with SARS-CoV-2 B.1.617.2 (Delta) variant in an elementary school

All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. No potential conflicts of interest were disclosed.