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The impact of reopening schools on community transmission of COVID-19 in January 2021


A new study published in Health Affairs uses ICES administrative health data to show that there was a small and manageable increase in COVID-19 cases following the reopening of schools in January 2021 in Ontario. 

The role of school closures as a strategy to slow the spread of COVID-19 has been fiercely debated, given the benefit of in-person learning for children and youth’s well-being and parents’ employment needs.

It is unclear how school closures have impacted COVID-19 transmission, because previous research has shown inconsistent results, likely due to concurrent public health interventions such as masking and social distancing.

“Many would argue that schools are the essential work of children, and that they should be the last to close and the first to open in the event of a pandemic lockdown,” says Tiffany Fitzpatrick, lead author and postdoctoral fellow at the Canadian Center for Vaccinology, Dalhousie University and former trainee at ICES. “Our study took advantage of a unique situation that occurred in Ontario, Canada to estimate how much school re-opening increased the number of COVID-19 cases in the wider community.”

In December 2020, Ontario entered a province-wide shutdown due to the COVID-19 pandemic, and a regionalized approach was taken to reopen schools for in-person instruction in January and February of 2021. All regions opted to wait until after schools reopened to relax gathering restrictions, and the province used a staggered approach to reopen the economy. 

Further to this, infection prevention and control mitigation strategies remained in place within schools. There was variability across school boards in the degree to which mitigation measures (such as masking, asymptomatic and rapid testing, and class cohorting) were implemented.

“Our study findings estimated that had schools not re-opened, only 213 fewer cases of COVID-19 would have occurred in Ontario between December 26, 2020 and February 28, 2021,” says Dr. Astrid Guttmann, co-senior author of the study, chief science officer at ICES. “That’s roughly 0.08% fewer cases than actually occurred.”

While increases in COVID-19 cases associated with school re-openings were small, they were particularly evident among children and youth and increased as more time passed beyond the re-open dates. 

Of note, this study took place during the second wave of the COVID-19 pandemic, before the circulation of variants of concern and at a time when community transmission was much lower than observed during other pandemic periods. As well, the COVID-19 vaccine was restricted to front-line health workers and those living and working in congregate living settings, such as long-term care facilities. Thus, these results may not be generalizable to other populations or other waves of the pandemic, as new variants may be more transmissible and can affect younger populations.

Though these additional COVID-19 cases in the community are to be expected with the resumption of in-person schooling, the research suggests that these risks are manageable with sufficient, layered mitigation strategies. The results also support the notion that schools should be the last to close and the first to reopen, and that interventions to reduce transmission in the community should be maintained in order to prioritize in-person learning.

The study “School reopening and COVID-19 in the community: evidence from a natural experiment in Ontario, Canada,” was published in Health Affairs.

Author block: Fitzpatrick T, Wilton A, Cohen E, Rosella L, Guttmann A.

ICES is an independent, non-profit research institute that uses population-based health information to produce knowledge on a broad range of healthcare issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting healthcare needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad, and is widely used by government, hospitals, planners, and practitioners to make decisions about care delivery and to develop policy. In October 2018, the institute formerly known as the Institute for Clinical Evaluative Sciences formally adopted the initialism ICES as its official name. For the latest ICES news, follow us on Twitter: @ICESOntario


Misty Pratt
Senior Communications Officer, ICES
[email protected]


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