Model-Estimated Association Between Simulated US Elementary School–Related SARS-CoV-2 Transmission, Mitigation Interventions, and Vaccine Coverage Across Local Incidence Levels

John Giardina,Benjamin P. Linas,Meagan C. Fitzpatrick,Andrea L. Ciaranello,Joshua Salomon,Alyssa Bilinski,Emily A. Kendall

doi:10.1001/jamanetworkopen.2021.47827

Abstract

With recent surges in COVID-19 incidence and vaccine authorization for children aged 5 to 11 years, elementary schools face decisions about requirements for masking and other mitigation measures. These decisions require explicit determination of community objectives (eg, acceptable risk level for in-school SARS-CoV-2 transmission) and quantitative estimates of the consequences of changing mitigation measures. To estimate the association between adding or removing in-school mitigation measures (eg, masks) and COVID-19 outcomes within an elementary school community at varying student vaccination and local incidence rates. This decision analytic model used an agent-based model to simulate SARS-CoV-2 transmission within a school community, with a simulated population of students, teachers and staff, and their household members (ie, immediate school community). Transmission was evaluated for a range of observed local COVID-19 incidence (0-50 cases per 100 000 residents per day, assuming 33% of all infections detected). The population used in the model reflected the mean size of a US elementary school, including 638 students and 60 educators and staff members in 6 grades with 5 classes per grade. Variant infectiousness (representing wild-type virus, Alpha variant, and Delta variant), mitigation effectiveness (0%-100% reduction in the in-school secondary attack rate, representing increasingly intensive combinations of mitigations including masking and ventilation), and student vaccination levels were varied. The main outcomes were (1) probability of at least 1 in-school transmission per month and (2) mean increase in total infections per month among the immediate school community associated with a reduction in mitigation; multiple decision thresholds were estimated for objectives associated with each outcome. Sensitivity analyses on adult vaccination uptake, vaccination effectiveness, and testing approaches (for selected scenarios) were conducted. With student vaccination coverage of 70% or less and moderate assumptions about mitigation effectiveness (eg, masking), mitigation could only be reduced when local case incidence was 14 or fewer cases per 100 000 residents per day to keep the mean additional cases associated with reducing mitigation to 5 or fewer cases per month. To keep the probability of any in-school transmission to less than 50% per month, the local case incidence would have to be 4 or fewer cases per 100 000 residents per day. In this study, in-school mitigation measures (eg, masks) and student vaccinations were associated with substantial reductions in transmissions and infections, but the level of reduction varied across local incidence. These findings underscore the potential role for responsive plans that deploy mitigation strategies based on local COVID-19 incidence, vaccine uptake, and explicit consideration of community objectives.

Highlights

To balance the educational and social and emotional benefits of in-person education with concerns about SARS-CoV-2 transmission in school settings, the US Centers for Disease Control and Prevention (CDC) recommends using a layered mitigation approach in kindergarten to 12th grade (K-12) schools
Thresholds for changing mitigation measures depended on the objective. Meaning These findings suggest that appropriate increases and decreases for in-school mitigation depend on policy makers’ goals; responsive plans, in which mitigation is deployed based on local COVID-19 incidence and vaccine uptake, may be appropriate
In this study, in-school mitigation measures and student vaccinations were associated with substantial reductions in transmissions and infections, but the level of reduction varied across local incidence

Summary

Introduction

To balance the educational and social and emotional benefits of in-person education with concerns about SARS-CoV-2 transmission in school settings, the US Centers for Disease Control and Prevention (CDC) recommends using a layered mitigation approach in kindergarten to 12th grade (K-12) schools Some components of this approach include vaccination for all eligible students and educators and staff, improved ventilation, and indoor masking regardless of vaccination status.[1] Individual states and school districts make local decisions about whether and how to incorporate these recommendations, and requirements for indoor masking have generated debate.[2] In communities with high vaccination rates and low COVID-19 incidence, or where masking is less widely accepted, many schools are considering removing masks and other elements of mitigation.[3,4]. While multiple studies indicate that masks are effective at mitigating the transmission of upper respiratory viruses,[5,6,7,8,9,10] they are generally viewed as a temporary measure.[11,12] Masks are physiologically safe, but there are limited data on the impact of mask-wearing on learning and social and emotional development, especially for younger children, students with special learning needs, and English language learners.[9,13] With the availability of vaccines for all US residents aged 5 years and older, many public health experts have called for “off-ramps” and “on-ramps” that use available public health data to inform decisions about when to remove or reinstate masking and other mitigation measures.[11,12,14,15]

Methods

Results

Discussion

Conclusion