RT Journal Article
SR Electronic
T1 Canadian SARS-CoV-2 serological survey using antenatal serum samples: a retrospective seroprevalence study
JF CMAJ Open
JO CMAJ
FD Canadian Medical Association
SP E305
OP E313
DO 10.9778/cmajo.20220045
VO 11
IS 2
A1 Andrea Atkinson
A1 Arianne Albert
A1 Elisabeth McClymont
A1 Janice Andrade
A1 Lori Beach
A1 Shelly Bolotin
A1 Isabelle Boucoiran
A1 Jared Bullard
A1 Carmen Charlton
A1 Joan Crane
A1 Shelley Dougan
A1 Jean-Claude Forest
A1 Greg J. German
A1 Yves Giguère
A1 Gabriel Girouard
A1 Catherine Hankins
A1 Mel Krajden
A1 Amanda Lang
A1 Paul Levett
A1 Jessica Minion
A1 Cory Neudorf
A1 Vanessa Poliquin
A1 Jason L. Robinson
A1 Heather Scott
A1 Derek R. Stein
A1 Vanessa Tran
A1 George Zahariadis
A1 Hong Y. Zhou
A1 Deborah Money
A1 The Antenatal Serostudies Team
YR 2023
UL http://www.cmajopen.ca/content/11/2/E305.abstract
AB Background: Insufficient data on the rate and distribution of SARS-CoV-2 infection in Canada has presented a substantial challenge to the public health response to the COVID-19 pandemic. Our objective was to assess SARS-CoV-2 seroprevalence in a representative sample of pregnant people throughout Canada, across multiple time points over 2 years of the pandemic, to describe the seroprevalence and show the ability of this process to provide prevalence estimates.Methods: This Canadian retrospective serological surveillance study used existing serological prenatal samples across 10 provinces over multiple time periods: Feb. 3–21, 2020; Aug. 24–Sept. 11, 2020; Nov. 16–Dec. 4, 2020; Nov. 15–Dec. 3, 2021; and results from the province of British Columbia during a period in which the SARS-CoV-2 B.1.1.529 (Omicron) variant was predominant, from Nov. 15, 2021, to June 11, 2022. Age and postal code administrative data allowed for comparison with concurrent polymerase chain reactivity (PCR)–positive results collected by Statistics Canada and the Canadian Surveillance of COVID-19 in Pregnancy (CANCOVID-Preg) project.Results: Seropositivity in antenatal serum as early as February 2020 indicates SARS-CoV-2 transmission before the World Health Organization’s declaration of the pandemic. Seroprevalence in our sample of pregnant people was 1.84 to 8.90 times higher than the recorded concurrent PCR-positive prevalence recorded among females aged 20–49 years in November–December 2020. Overall seropositivity in our sample of pregnant people was low at the end of 2020, increasing to 15% in 1 province by the end of 2021. Seroprevalence among pregnant people in BC during the Omicron period increased from 5.8% to 43% from November 2021 to June 2022.Interpretation: These results indicate widespread vulnerability to SARS-CoV-2 infection before vaccine availability in Canada. During the time periods sampled, public health tracking systems were under-reporting infections, and seroprevalence results during the Omicron period indicate extensive community spread of SARS-CoV-2 infection.