Modifications to student quarantine policies in K-12 schools implementing multiple COVID-19 prevention strategies restores in-person education without increasing SARS-CoV-2 transmission risk, January-March 2021

Abstract

Objective: To determine whether modified K-12 student quarantine policies that allow some students to continue in-person education during their quarantine period increase schoolwide SARS-CoV-2 transmission risk following the increase in cases in winter 2020-2021.

Methods: We conducted a prospective cohort study of COVID-19 cases and close contacts among students and staff (n = 65,621) in 103 Missouri public schools. Participants were offered free, saliva-based RT-PCR testing. The projected number of school-based transmission events among untested close contacts was extrapolated from the percentage of events detected among tested asymptomatic close contacts and summed with the number of detected events for a projected total. An adjusted Cox regression model compared hazard rates of school-based SARS-CoV-2 infections between schools with a modified versus standard quarantine policy.

Results: From January-March 2021, a projected 23 (1%) school-based transmission events occurred among 1,636 school close contacts. There was no difference in the adjusted hazard rates of school-based SARS-CoV-2 infections between schools with a modified versus standard quarantine policy (hazard ratio = 1.00; 95% confidence interval: 0.97-1.03).

Discussion: School-based SARS-CoV-2 transmission was rare in 103 K-12 schools implementing multiple COVID-19 prevention strategies. Modified student quarantine policies were not associated with increased school incidence of COVID-19. Modifications to student quarantine policies may be a useful strategy for K-12 schools to safely reduce disruptions to in-person education during times of increased COVID-19 community incidence.

Fig 1. Primary reasons close contacts of persons with COVID-19 (n = 345) were deemed ineligible for modified quarantine by K–12 school officials, Greene County, Missouri, January 25–March 21, 2021.

Abbreviations: COVID-19 = coronavirus disease 2019; K–12 = kindergarten through grade 12. The number inside a rectangle corresponds to the number of close contacts who were deemed ineligible for a modified quarantine based on the category below the rectangle. Rectangles that overlap two reasons indicate both reasons were cited in the decision to deem the individual ineligible for a modified quarantine. *Under Greene County’s modified quarantine policy, only students aged ≤18 years were eligible for a modified quarantine. † Prolonged direct contact was defined as direct physical contact with the person having COVID-19 for ≥15 minutes. ‡ Includes 7 contacts who were also ineligible due to extracurricular activities and 2 contacts who were also ineligible due to contact outside of school.

Fig 2. Adjusted probability of school-based SARS-CoV-2 infections based on total projected cases (n = 23) in schools with and without a modified quarantine policy, Greene and St. Louis Counties, Missouri, January 25–March 21, 2021.

Top-right inset shows zoomed-in view of adjusted probability curves over the study period. The adjusted* probability curve of school-based SARS-CoV-2 infection in schools with a standard quarantine policy is shown by the teal line; in schools with a modified quarantine policy, it is shown by the dotted black line. The adjusted probability curves and 95% confidence intervals were the same for schools with and without a modified quarantine policy. * The Cox regression model was adjusted for potential school-level confounding factors: quartiles of the percentage of students eligible to receive free or reduced-price lunch (as a proxy for school resources) and the school’s total number of cases that attended school or a school-related event during the study period.