A blood donor seroprevalence study, conducted by Héma-Québec in collaboration with the Institut national de santé publique (INSPQ), reveals that 2.23% of blood donors were infected with the COVID-19 virus.
The purpose of the study, which involved a sample of 7,691 people aged 18 to 69 who donated blood between May 25 and July 9, was to estimate the percentage of people who contracted the virus in Quebec.
Based on the results, the study extrapolated that about 124,880 people in the age group in question contracted the virus since the beginning of the pandemic. The Ministère de la Santé et des Services sociaux du Québec, which sponsored the research, reported about 37,000 cases for the 20 to 69 age group for the same period.
Not surprisingly, the highest rates were observed in the Montreal and Laval regions, at 3.05%.
The study also shows that the Mauricie-Centre-du-Québec region, which had a reported COVID-19 rate that was three times lower than in Montreal or Laval, nevertheless had an almost identical seroprevalence of 2.96%.
As for the rest of Quebec (excluding Montreal and its surrounding areas), seroprevalence was much lower at 1.29%.
In order to properly reflect the percentage Quebeckers who developed antibodies against the COVID-19 virus, study participants were selected from 12 of the 18 health regions. The remaining six regions were not included since there was no blood collection during the recruitment period. These blood donors comprised a representative group of the general population. Héma-Québec had the capacity to conduct such a study since it already systematically collects blood samples from each blood donation and has the laboratories and expertise to carry out these tests.
The 173 donors in whom antibodies were detected will be contacted to document their symptoms and the possible source of infection. An equivalent number of donors with negative test results will also be questioned. This process will help estimate the percentage of infected people who were asymptomatic (results to come).
Lastly, in order to continue monitoring the evolution of COVID-19 in Quebec, the study may be repeated on a regular basis until the end of the pandemic.