This is a summary, written by members of the CITF Secretariat, of:
Goldfarb DM, Mâsse LC, Watts AW, Hutchison SM, Muttucomaroe L, Bosman ES, Barakauskas VE, Choi A, Irvine MA, Reicherz F, Coombs D, O’Reilly C, Sediqi S, Razzaghian HR, Sadarangani M, O’Brien SF, Lavoie PM. SARS-CoV-2 seroprevalence among Vancouver public school staff in British Columbia, Canada. medRxiv. 2021 Jun 18. doi: 10.1101/2021.06.16.21258861.
The results and/or conclusions contained in the research do not necessarily reflect the views of all CITF members.
Drs. Pascal Lavoie and Louise C. Mâsse and their team at the University of British Columbia have released interim results, soon to be submitted for peer-review, suggesting that school staff are not at increased risk of SARS-CoV-2 infection at school, compared to in the community. The authors attribute this in part to the appropriate public health measures in place. Participants in their recent SARS-CoV-2 serosurvey included school staff employed at the Vancouver School Board. The study found that the percentage of individuals infected with SARS-CoV-2 within the school system was similar to that found in the local community.
What are serosurveys?
Serosurveys assess the presence of antibodies in people’s blood, in this case, those recognizing SARS-CoV-2, the virus that causes COVID-19, to determine if they were previously infected. Since many people have few or no symptoms, infected individuals may never know they are infected. For this reason, population-based serosurveys are considered a valuable tool in estimating the seroprevalence, i.e. the proportion of the population previously infected with SARS-CoV-2.
- Seroprevalence of school staff was 2.3%, which was the same as the rate found in blood donor controls in the community.
- Between the start of the pandemic and March 4, 2021, 0.98% of students and 1.3% of staff tested positive for active infections with SARS-CoV-2.
Drs. Lavoie and Mâsse’s study aimed to a) determine the percentage of adult staff working in the Vancouver School Board district with antibodies to SARS-CoV-2, and b) to assess the staff’s occupational risk for SARS-CoV-2 infection during in-person schooling between September 2020 and May 7, 2021. The study enrolled 1,689 participants, many of them working in classrooms (78.2%). Of these, most worked in elementary schools (64%) and secondary schools (28%), with a few working with several grade levels or at the School Board office (8.3%).
The serology test used in this serosurvey was able to distinguish between antibodies due to a COVID-19 infection and antibodies produced after receiving a COVID-19 vaccine. Of the 1,556 participants tested (92.1% of total cohort), 35 showed evidence of a past infection with SARS-CoV-2. The resulting seroprevalence rate of 2.3% was the same as the seroprevalence rate found in the reference group (people from the community not working in schools with a similar profile of age, sex and area of residence). Additionally, although as many as 278 school staff reported a close contact with a COVID-19 case, only 24 (incidence rate of 1.4%) tested positive for the virus through PCR testing (usually a nasal swab, detects an active infection) and only five (21%) of those people believed they had acquired the infection at school. Seven of the 24 (29%) people infected with SARS-CoV-2 reported close contact with a friend or family member with COVID-19, with one (4%) who reported close contact with both a co-worker and family member with COVID-19. The remaining 11 (46%) were not aware of any close contact with a COVID-19 case or the source ofinfection.
The study team has concluded that despite a high perception of potential exposure in school settings, the percentage of infected individuals within Vancouver public schools is similar to that of the local community. They maintain that with appropriate precautions in place, including protocols for testing and contract tracing, in-person schooling is not associated with a significantly increased risk of SARS-CoV-2 infection, even for classroom-based staff.
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