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Published on: February 16, 2022
SARS-CoV-2 seroprevalence among blood donors after the first COVID-19 wave in Canada
Sahar Saeed1, Steven J Drews2,3, Chantale Pambrun4,5
1Epidemiology and Surveillance, Canadian Blood Services, Ottawa, Ontario, Canada.
Insights
COVID-19 seroprevalence in Canadian blood donors was 7.0/1000, with higher rates in Ontario and among ethnic minorities. This highlights regional disparities and the value of blood services in public health surveillance.
Area of Science:
- Immunology
- Epidemiology
- Public Health
Background:
- Case detection underestimates the true burden of COVID-19.
- Blood services can support public health by estimating seroprevalence.
- This study estimated SARS-CoV-2 seroprevalence post-first wave in Canada.
Purpose of the Study:
- To estimate the seroprevalence of SARS-CoV-2 IgG antibodies among Canadian blood donors.
- To identify regional, demographic, and socioeconomic disparities in seroprevalence.
- To evaluate temporal trends in seroprevalence.
Main Methods:
- Serial cross-sectional study of blood donors from May 9 to July 21, 2020.
- Used Abbott Architect assay for SARS-CoV-2 IgG detection in retention plasma.
- Standardized seroprevalence to population demographics and adjusted for assay characteristics using Rogan-Gladen.
Main Results:
- Adjusted seroprevalence was 7.0/1000 donors (95% CI; 6.3, 7.6).
- Prevalence varied geographically, with Ontario having the highest rate (8.8/1000) and the Atlantic region the lowest (4.5/1000).
- Ethnic minority donors had higher seroreactivity (aOR 1.5) than white donors; no temporal trends were observed.
Conclusions:
- Over 99% of Canadian blood donors lacked evidence of past SARS-CoV-2 infection.
- Significant regional variability and ethnic disparities in seroprevalence were identified.
- Seroprevalence studies are crucial for monitoring public health trends and disparities.
Background:
Case detection underestimates the burden of the COVID-19 pandemic. Following the first COVID-19 wave, we estimated the seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among blood donors across Canada.
Study Design And Methods:
This serial cross-sectional study was conducted between May 9 and July 21, 2020 from blood donors donating at all Canadian Blood Services locations. We used the Abbott Architect assay to detect SARS-CoV-2 IgG antibodies from retention plasma. Seroprevalence was standardized to population-level demographics and assay characteristics were adjusted using the Rogan-Gladen equation. Results were stratified by region, age, ethnicity, ABO groups, and quantiles of material and social deprivation indices. Temporal trends were evaluated at 2-week intervals. Univariate and multivariate logistic regression compared SARS-CoV-2 reactive to non-reactive donors by sociodemographic variables.
Results:
Overall 552/74642 donors, had detectable antibodies, adjusted seroprevalence was 7.0/1000 donors (95% CI; 6.3, 7.6). Prevalence was differential by geography, Ontario had the highest rate, 8.8/1000 donors (7.8, 9.8), compared to the Atlantic region 4.5/1000 donors (2.6, 6.4); adjusted odds ratio (aOR) 2.2 (1.5, 3.3). Donors that self-identified as an ethnic minority were more likely than white donors to be sero-reactive aOR 1.5 (1.2, 1.9). No temporal trends were observed.
Discussion:
Worldwide, blood services have leveraged their operational capacity to inform public health. While >99% of Canadians did not show humoral evidence of past infection, we found regional variability and disparities by ethnicity. Seroprevalence studies will continue to play a pivotal role in evaluating public health policies by identifying trends and monitor disparities.
