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Large US evaluation of school closures' effect on spread of COVID

Schools can reopen for in-person learning without substantially increasing community case rates of SARS-CoV-2, found national, retrospective cohort study in the US, published in Nature Medicine.

During the first few months of the COVID-19 pandemic, primary and secondary schools in the United States were closed to in-person education as part of the national response to control the spread of SARS-CoV-2. This decision was guided by data extrapolated from influenza transmission models, which suggested school closures as an effective measure for reducing the basic reproductive number of respiratory viral infections, and early evidence suggesting that non-pharmaceutical public health interventions, including school closures, were associated with improved SARS-CoV-2 outbreak control.

Modelling studies and time series analyses from across the world differ in their assessment of the impact of reopening schools on community SARS-CoV-2 transmission. Elementary school children are at lower risk of severe illness than other age groups and their role in driving transmission in the community is cloudy. However, there are multiple close interactions between individuals from separate households in a school setting; thus, interactions that occur in schools, even if each contact is lower risk, may contribute to SARS-CoV-2 spread. If children and school staff become infected at school, these transmissions may lead to subsequent transmissions to family and other contacts, potentially resulting in increases in community transmission of SARS-CoV-2.

Recently published studies about the impact of school mode on community transmission from Indiana, Texas and other states found conflicting results, with some analyses suggesting substantial increases in case rates associated with school openings, others suggesting a small impact, and still others suggesting that opening schools to in-person learning has no impact on community case rates after adjusting for community incidence and minimal impact on hospitalisation rates when COVID-19 hospitalisations within a county are kept under 36–44 per 100,000.

Thus, the association between type of school reopening mode (for example, virtual, hybrid or in-person) and community spread of COVID continues to be a critical policy question. Although school closure early in the pandemic was associated with lower SARS-CoV-2 incidence, the impact of these closures in addition to other public infection prevention measures, such as business restrictions, social distancing, masking, scaling up of testing and contact tracing, is unknown.

The aim of this study was to evaluate the impact of school mode and opening to in-person education on subsequent changes in community incidence of SARS-CoV-2.

The research team involved in the study were from various institutions: Harvard Medical School; University of Utah School of Medicine; Binghamton University; State University of New York; Beth Israel Deaconess Medical Center, Boston; Matheson Center for Health Care Studies, University of Utah; Center for Access & Delivery Research and Evaluation, Iowa City VA Health Care System; Carver College of MedicineThe University of Iowa; Brown University Watson Institute for International and Public Affairs; VA Boston Center for Healthcare Organization and Implementation Research (CHOIR).

Study details

The impact of school opening model on SARS-CoV-2 community incidence and mortality

Zeynep Ertem, Elissa Schechter-Perkins, Emily Oster, Polly van den Berg, Isabella Epshtein, Nathorn Chaiyakunapruk, Fernando Wilson, Eli Perencevich, Warren Pettey, Westyn Branch-Elliman & Richard Nelson.

Published in Nature Medicine on 27 October 2021

Abstract
The role that traditional and hybrid in-person schooling modes contribute to the community incidence of SARS-CoV-2 infections relative to fully remote schooling is unknown. We conducted an event study using a retrospective nationwide cohort evaluating the effect of school mode on SARS-CoV-2 cases during the 12 weeks after school opening (July–September 2020, before the Delta variant was predominant), stratified by US Census region. After controlling for case rate trends before school start, state-level mitigation measures and community activity level, SARS-CoV-2 incidence rates were not statistically different in counties with in-person learning versus remote school modes in most regions of the United States.

In the South, there was a significant and sustained increase in cases per week among counties that opened in a hybrid or traditional mode versus remote, with weekly effects ranging from 9.8 (95% confidence interval (CI) = 2.7–16.1) to 21.3 (95% CI = 9.9–32.7) additional cases per 100,000 persons, driven by increasing cases among 0–9 year olds and adults. Schools can reopen for in-person learning without substantially increasing community case rates of SARS-CoV-2; however, the impacts are variable. Additional studies are needed to elucidate the underlying reasons for the observed regional differences more fully.

 

Nature Medicine article – The impact of school opening model on SARS-CoV-2 community incidence and mortality (Restricted access)

 

See more from MedicalBrief archives:

 

COVID lessons from a contrarian Sweden

 

Masks helped limit COVID transmission in unvaccinated students — US study

 

Schools guidance to reflect new evidence on distancing in classrooms — CDC

 

COVID-19 in children: The South African experience and way forward

 

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