Antibody Reactivity Against SARS-CoV-2 in Adults from the Vancouver Metropolitan Area, Canada

Abstract

Background: Quantifying antibody reactivity against multiple SARS-CoV-2 antigens at the population level may help understand individual differences in COVID-19 severity. Pre-existing low antibody cross-reactivity may be particularly prevalent among childcare providers, including pediatric health care workers (HCW) who may be more exposed to circulating coronaviruses.Methods: Cross-sectional study that included adults in the Vancouver area in British Columbia (BC), Canada, between May 17 and June 19, 2020. SARS-CoV-2 seroprevalence was ascertained by measuring total SARS-CoV-2 IgG/M/A antibodies against a recombinant spike (S1) protein and adjusted for bias due to false-positive and false-negative test results. A novel, high sensitivity multiplex assay was also used to profile IgG against four SARS-CoV-2 antigens, SARS-CoV and four circulating coronaviruses.Findings: Among 276 participants (71% HCW), three showed evidence of direct viral exposure, yielding an adjusted seroprevalence of 0.60% [95%CI 0% – 2.71%], with no difference between HCW and non-HCW, or between paediatric and adult HCW. Among the 273 unexposed individuals, 7.3% [95%CI 4.5% – 11.1%], 48.7 [95%CI 42.7% – 54.8%] and 82.4% [95%CI 77.4% – 86.7%] showed antibody reactivity against SARS-CoV-2 RBD, N or Spike proteins, respectively. SARS-CoV-2 reactivity did not significantly correlate with age, sex, did not significantly differ between HCW and non-HCW (prevalence 1.0% vs 1.0%; P =1.00) and between pediatric and adult HCW (0.7% vs 1.6%; P =0.54), and modestly correlated with reactivity to circulating coronaviruses (Spearman rho range: 0.130 to 0.224 for 7 significant (FDR 5%), out of 16 correlations, from 36 correlations tested).Interpretation: A substantial proportion of individuals showed low, but detectable antibody reactivity against SARS-CoV-2 antigens in this population despite low evidence of direct SARS-CoV-2 exposure.Funding Statement: This study was funded by unrestricted funding to PML and an Intramural Research Program of the Vaccine Research Centre (VRC) at the National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH)Declaration of Interests: The authors declare no conflicts of interest.Ethics Approval Statement: The study was approved by the University of British Columbia Children’s & Women’s Research Ethic Board (H20-01205).