COVID-19 population-based analysis of the 2020–2021 school year in Saskatchewan

Abstract

Background: The coronavirus disease 2019 (COVID-19) pandemic has caused substantial disruption to in-person learning, often interfering with the social and educational experience of children and youth across North America, and frequently impacting the greater community by limiting the ability of parents and caregivers to work outside the home. Real-world evidence related to the risk of COVID-19 transmission in school settings can help inform decisions around initiating, continuing, or suspending in-person learning.

Methods: We analyzed routinely collected case-based surveillance data from Saskatchewan’s electronic integrated public health system, Panorama, from the 2020–2021 school year, spanning various phases of the pandemic (including the Alpha variant wave), to better understand the risk of in-school transmission of COVID-19 in Saskatchewan schools.

Results: The majority (over 80%) of school-associated COVID-19 infections were acquired outside the school setting. This finding suggests that the non-pharmaceutical measures in place (including masking, distancing, enhanced hygiene, and cohorting) worked to limit viral spread in schools.

Conclusion: Implementation of such control measures may play an essential role in allowing children and youth to safely maintain in-person learning during the pandemic.

Introduction

Since the start of the coronavirus disease 2019 (COVID-19) pandemic in North America, the question of whether schools can safely operate in-person has been the focus of much debate. Schools were frequently included in widespread shutdowns to limit viral transmission and exponential growth, despite a lack of evidence related to their role in transmission. Stakeholders, including parents, educators, public health professionals, and the media, have presented many differing viewpoints on the risks/benefits of in-person learning during the pandemic. The issue remains at the forefront during the third school year affected by COVID-19.

Prior to start of the 2020–2021 school year, there was little real-world evidence related to in-person learning and the risk of COVID-19 transmission. Evidence has been emerging since that time, however, and we now have a better understanding of COVID-19 transmission dynamics in schools in a variety of geographic settings^{Footnote 1Footnote 2Footnote 3Footnote 4Footnote 5Footnote 6Footnote 7Footnote 8Footnote 9Footnote 10}. Several of these studies have found that with appropriate mitigation measures in place (such as cohorting, distancing, or masking), the risk of in-school transmission was relatively low. A study of 17 rural Wisconsin schools found that of COVID-19 cases identified among students, only 3.7% were acquired in the school setting^{Footnote 2}. One report of a large outbreak in a Jerusalem high school concluded that crowded classrooms, the suspension of masking requirements (due to a heatwave), and continuous air conditioning were factors that substantially increased transmission. However, attack rates among students and staff were still relatively low at 13.2% and 16.6%^{Footnote 4}. Data from British Columbia found a similar proportion of overall school-associated cases were likely acquired in school (13.0%)^{Footnote 8}. Another British Columbia study reported that in-person schooling was not associated with an increased risk of COVID-19 acquisition among school staff^{Footnote 1}, and other Canadian and United States studies have reported relatively low risk associated with in-person schooling as well^{Footnote 6Footnote 9}. Here we present the characteristics of cases and risk of transmission of COVID-19 in preschools, elementary, and high schools in Saskatchewan, a jurisdiction that largely maintained in-person learning throughout the 2020–2021 school year.

Methods

We analyzed population-level data from the 2020–2021 school year in Saskatchewan, spanning various phases of the pandemic (including the Alpha variant wave), to better understand the risk of in-school transmission of COVID-19 in Saskatchewan schools.

Routinely collected case-based surveillance data from Saskatchewan’s electronic integrated public health system, Panorama, were used for the analysis. Data on all laboratory-confirmed COVID-19 cases were entered in Panorama, and standardized data collection worksheets are used for case and contact investigations. These surveillance data were used to better understand the epidemiology of COVID-19, including case volumes over time, demographics and case type (e.g. staff versus student), and most likely exposure sources for cases.

The study period for the 2020–2021 school year was from September 2, 2020 (start of school year) to July 12, 2021 (approximately two weeks post the end of the school year). Data were extracted on July 13, 2021, and analyzed using IBM SPSS Statistics 22.0 and Microsoft Excel 2016. This analysis represents a synthesis of province-wide data from the full 2020–2021 school year; similar analyses were conducted throughout the school year at the local and provincial level and were used to inform decisions around maintaining in-person learning.

“School-associated” cases were identified using risk factor variables routinely collected during case investigations that indicate whether a person was a teacher, a preschool attendee, a school attendee (e.g. K–12) or other school staff. We included only those school-associated cases that had a most likely source (MLS) of exposure flagged in Panorama, which is also routinely collected during case interviews, as determined by trained case investigators, who are typically public health nursing staff. The determination is based on a thorough retrospective investigation, taking into account the incubation period of the organism, period of communicability, and all potential exposure settings during the relevant time period for acquisition. Ultimately the investigator makes the determination of which reported exposure is the most likely source of infection.

Results

From September 3, 2020, through July 12, 2021, a total of 5,952 school-associated cases occurred in Saskatchewan. Among these, 4,980 (83.7%) had MLS data available; this analysis is based on those 4,980 cases. Of these cases, the largest proportion occurred among children aged 5–13 years (n=2,336, 46.9%), followed by youth aged 14–19 years (n=1,470, 29.5%). Other age groups made up substantially smaller proportions of the overall caseload (Table 1).

By category, the majority of cases (n=3,853, 77.4%) were among elementary/high school students, with smaller proportions comprising teachers (n=491, 9.9%), other school staff (n=420, 8.4%), and preschool students (n=216, 4.3%). Teachers had the highest proportion of in-school exposures (n=112, 22.8%), followed by elementary/high school students (n=614, 15.9%), other school staff (n=65, 15.5%), and preschool students (n=25, 11.6%) (Table 2). Throughout the academic year, 816 (16.4%) school-associated cases were found to have acquired their infection in the school, with household exposure (n=2,810, 56.4%) being responsible for the majority of infections (Figure 1).

The epidemic curve of school-associated COVID-19 cases during the 2020–2021 school year (Figure 2) illustrates that while the volume of school-associated cases (height of the bars) varied throughout the time period, the proportion of infections acquired in school (green portion of the bars, also shown as a percent by the red line) remained relatively stable throughout the period. Of note, the Alpha variant was first identified in Saskatchewan in February 2021, and led to a subsequent surge in infections by mid-March. This surge was clearly reflected among school-associated cases on the epidemic curve, beginning the week of March 14–20; however, the overall proportion of cases attributed to in-school exposure remained relatively steady throughout this surge in cases.