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Abstract

Background

Serosurveys for SARS-CoV-2 aim to estimate the proportion of the population that has been infected.

Aim

This observational study assesses the seroprevalence of SARS-CoV-2 antibodies in Ontario, Canada during the first pandemic wave.

Methods

Using an orthogonal approach, we tested 8,902 residual specimens from the Public Health Ontario laboratory over three time periods during March–June 2020 and stratified results by age group, sex and region. We adjusted for antibody test sensitivity/specificity and compared with reported PCR-confirmed COVID-19 cases.

Results

Adjusted seroprevalence was 0.5% (95% confidence interval (CI): 0.1–1.5) from 27 March–30 April, 1.5% (95% CI: 0.7–2.2) from 26–31 May, and 1.1% (95% CI: 0.8–1.3) from 5–30 June 2020. Adjusted estimates were highest in individuals aged ≥ 60 years in March–April (1.3%; 95% CI: 0.2–4.6), in those aged 20–59 years in May (2.1%; 95% CI: 0.8–3.4) and in those aged ≥ 60 years in June (1.6%; 95% CI: 1.1–2.1). Regional seroprevalence varied, and was highest for Toronto in March–April (0.9%; 95% CI: 0.1–3.1), for Toronto in May (3.2%; 95% CI: 1.0–5.3) and for Toronto (1.5%; 95% CI: 0.9–2.1) and Central East in June (1.5%; 95% CI: 1.0–2.0). We estimate that COVID-19 cases detected by PCR in Ontario underestimated SARS-CoV-2 infections by a factor of 4.9.

Conclusions

Our results indicate low population seroprevalence in Ontario, suggesting that public health measures were effective at limiting the spread of SARS-CoV-2 during the first pandemic wave.

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This work is licensed under a Creative Commons Attribution 4.0 International License.
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2021-12-16
2024-12-26
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Assessment of population infection with SARS-CoV-2 in Ontario, Canada, March to June 2020
<p class="citation"> <span>Citation style for this article:</span> <span class="meta-value authors"> <a href="/search?value1=Shelly+Bolotin&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Bolotin Shelly</a>, <a href="/search?value1=Vanessa+Tran&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Tran Vanessa</a>, <a href="/search?value1=Shelley+L+Deeks&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Deeks Shelley L</a>, <a href="/search?value1=Adriana+Peci&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Peci Adriana</a>, <a href="/search?value1=Kevin+A+Brown&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Brown Kevin A</a>, <a href="/search?value1=Sarah+A+Buchan&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Buchan Sarah A</a>, <a href="/search?value1=Katherene+Ogbulafor&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Ogbulafor Katherene</a>, <a href="/search?value1=Tubani+Ramoutar&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Ramoutar Tubani</a>, <a href="/search?value1=Michelle+Nguyen&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Nguyen Michelle</a>, <a href="/search?value1=Rakesh+Thakkar&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Thakkar Rakesh</a>, <a href="/search?value1=Reynato+DelaCruz&option1=author&noRedirect=true" class="nonDisambigAuthorLink">DelaCruz Reynato</a>, <a href="/search?value1=Reem+Mustfa&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Mustfa Reem</a>, <a href="/search?value1=Jocelyn+Maregmen&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Maregmen Jocelyn</a>, <a href="/search?value1=Orville+Woods&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Woods Orville</a>, <a href="/search?value1=Ted+Krasna&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Krasna Ted</a>, <a href="/search?value1=Kirby+Cronin&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Cronin Kirby</a>, <a href="/search?value1=Selma+Osman&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Osman Selma</a>, <a href="/search?value1=Eugene+Joh&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Joh Eugene</a>, <a href="/search?value1=Vanessa+G+Allen&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Allen Vanessa G</a></span>. Assessment of population infection with SARS-CoV-2 in Ontario, Canada, March to June 2020. <a href="/content/ecdc">Euro Surveill.</a> 2021;26(50):pii=2001559. <a href="https://doi.org/10.2807/1560-7917.ES.2021.26.50.2001559" title="doi link" target="_blank">https://doi.org/10.2807/1560-7917.ES.2021.26.50.2001559</a> <span class="ES_Article_citation"> <span class="generated">Received</span>: 18 Aug 2020;&nbsp;&nbsp; <span class="generated">Accepted</span>: 14 Mar 2021 </span> </p>
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