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Observational Study
. 2025 Jun 11;54(4):dyaf113.
doi: 10.1093/ije/dyaf113.

School opening associated with lower test-adjusted COVID-19 case rates in children

Ambarish Chandra  1   2 , Tracy B Høeg  3
Affiliations
Observational Study

School opening associated with lower test-adjusted COVID-19 case rates in children

Ambarish Chandra et al. Int J Epidemiol. .

Abstract

Background: There is conflicting evidence from prior studies on the relationship between in-person schooling and transmission of SARS-CoV-2 among children. This may be due to multiple confounders in estimating this relationship, including the decision to close schools, community rates of infection, and rates of testing.

Methods: Regression-based observational study to estimate the relationship between school openings and COVID-19 case rates among children, while accounting for potential confounders including community case rates, mitigations in schools, and rates of testing among schoolchildren. The setting is US school districts in the Fall of 2021, from 3 weeks prior through 12 weeks after school opening, using restricted data obtained from the Centers for Disease Control and Prevention. Data were available for school districts in 2592 counties, containing 86% of the US population.

Results: School openings were associated with a brief rise in cases among children relative to adults, with a peak of 39.3 [37.7, 40.9] additional cases per 100 000 per week. However, children were tested at higher rates when schools were in session. After adjusting for testing rates, case rates among children were significantly lower after schools reopened by 4.7 cases per 100 000 compared with over summer break.

Conclusion: School reopening in the USA in the 2021-22 academic year was accompanied by an increase in SARS-CoV-2 testing in children and a brief rise in pediatric cases. When testing rates are accounted for, school reopening was associated with a decrease in COVID-19 cases among children relative to adults. A lower threshold for testing in the school setting may be an important confounder in studies of SARS-CoV-2 transmission.

Keywords: COVID-19; SARS-CoV-2 transmission; confounding; school openings; testing rates.

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Conflict of interest statement

None declared.

Figures

Figure 1.
Figure 1.
Estimated school-week fixed-effects from a regression of weekly per-capita cases of COVID-19 among ages 0–19, from 3 weeks prior to the start of the school year until 12 weeks after school opening. Control variables included: adult cases in the corresponding county and week, pediatric vaccination rates, and county-level demographic variables. Case rates for 3 weeks prior to school start are normalized to zero. 95% Confidence intervals are shown shaded.
Figure 2.
Figure 2.
Estimated school-week fixed-effects from a regression of weekly per-capita cases of COVID-19 among ages 0–19, from 3 weeks prior to the start of the school year until 12 weeks after school opening, stratified by US Census region. Other details are as in Fig. 1.
Figure 3.
Figure 3.
Estimated school-week fixed-effects from a regression of weekly per-capita cases of COVID-19 among ages 0–19, from 3 weeks prior to the start of the school year until 12 weeks after school opening, stratified by county mask mandate status. Analysis based on 1832 counties with unambiguous data on school mask mandates. Other details are as in Fig. 1.
Figure 4.
Figure 4.
Share of reported tests and cases in children, as a proportion of the total in the population. Dashed vertical lines denote the median week of school opening in each jurisdiction. Children are defined according to the following age groups: New York: 5–19; Florida: 0–19; Georgia: 5–17; Chicago: 0–17. r refers to Pearson’s correlation coefficient.
Figure 5.
Figure 5.
Estimated school-week fixed-effects from a regression of weekly per-capita cases of COVID-19 among ages 0–19, from 3 weeks prior to the start of the school year until 12 weeks after school opening, with and without adjusting for testing rates in children. Analysis based on four jurisdictions that provide age stratified rates of testing. Other details are as in Fig. 1.
Figure 6.
Figure 6.
Hospitalizations among children in New York and Georgia, as well as the average for 13 states, June 2021–June 2022. Dashed vertical lines denote the dates of school opening in NY and GA in the Fall of 2021. Source: Centers for Disease Control COVID-NET Hospitalization Surveillance Network for 13 states.
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References

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