Assessing K-12 school reopenings under different COVID-19 Spread scenarios - United States, school year 2020/21: A retrospective modeling study

Abstract

Introduction: School-age children play a key role in the spread of airborne viruses like influenza due to the prolonged and close contacts they have in school settings. As a result, school closures and other non-pharmaceutical interventions were recommended as the first line of defense in response to the novel coronavirus pandemic (COVID-19).

Methods: We used an agent-based model that simulates communities across the United States including daycares, primary, and secondary schools to quantify the relative health outcomes of reopening schools for the period of August 15, 2020 to April 11, 2021. Our simulation was carried out in early September 2020 and was based on the latest (at the time) Centers for Disease Control and Prevention (CDC)'s Pandemic Planning Scenarios released in May 2020. We explored different reopening scenarios including virtual learning, in-person school, and several hybrid options that stratify the student population into cohorts in order to reduce exposure and pathogen spread.

Results: Scenarios where cohorts of students return to school in non-overlapping formats, which we refer to as hybrid scenarios, resulted in significant decreases in the percentage of symptomatic individuals with COVID-19, by as much as 75%. These hybrid scenarios have only slightly more negative health impacts of COVID-19 compared to implementing a 100% virtual learning scenario. Hybrid scenarios can significantly avert the number of COVID-19 cases at the national scale-approximately between 28 M and 60 M depending on the scenario-over the simulated eight-month period. We found the results of our simulations to be highly dependent on the number of workplaces assumed to be open for in-person business, as well as the initial level of COVID-19 incidence within the simulated community.

Conclusion: In an evolving pandemic, while a large proportion of people remain susceptible, reducing the number of students attending school leads to better health outcomes; part-time in-classroom education substantially reduces health risks.

Keywords: Agent-based model; COVID-19; K-12 school reopening scenarios; Non-pharmaceutical interventions; Workplace restrictions.

Graphical abstract

Fig. 1

National results from the EpiCast model for various school reopening scenarios under Fewer Open Workplaces and More Open Workplaces (simulation period: August 15, 2020 to April 11, 2021).

Fig. 2

Simulated results of cumulative cases per county per 100,000 population for (1) two non-overlapping cohorts of 40% of students attending school 2-days a week and (2) 80% of students in-classroom learning (simulation period: August 15, 2020 to April 11, 2021).

Fig. 3

Source of infection for scenarios aggregated for all states.

Fig. 4

School-related source of infection breakdown including playgroup, daycare, student-student, teacher- student, student-student. The largest contribution is generated from the student-student interactions.

Fig. 5

Cases averted and delay to peak incidence in days for all national-level scenarios. Fewer people physically at work and more social distancing along with hybrid school scenarios avert a significant number of cases and delay the peak; fully offsite learning averts even more cases and almost doubles the delay to peak compared to hybrid school scenarios.