Sex differences of COVID-19 serological response of individuals infected, vaccinated, or those with hybrid immunity in Ontario.

Differences in COVID-19 infections were well known to vary by sex early in the COVID-19 pandemic; older males with comorbid conditions were experiencing more severe outcomes compared to females. As individuals continue to get infected with the COVID-19 virus, instances of long COVID syndrome are becoming more common and in contrast, more so in females. A preliminary report by Statistics Canada and the Public Health Agency of Canada found that 18% of female adults who tested positive or had a suspected COVID-19 infection reported developing the syndrome. These sex differences are known to be driven by well known discrepancies in immunologic response. However, sex differences in long-term immunity have not been re-evaluated since the introduction of mass vaccination programs. As such, this study will evaluate the long-term effectiveness of vaccine immunity and infection-acquired immunity by assessing the association of long-term immune protection by sex from 2021-2022 in Ontario. Data for this project has already been collected via the COVID-19 Immunity Task Force, including serology data from the Canadian Blood Services and de-identified sex information from the Ontario Registered Persons Database. The serology information comes from donated blood samples that were randomly tested for COVID-19 antibodies. Based on the results, samples were classed as infected with SARS-CoV-2 or as vaccinated. Our analyses will evaluate the association between sex and antibody response. Data from individuals who have donated multiple times and show hybrid immunity, an instance of viral infection and another instance of vaccine antibodies (or vice-versa), will also be included. This study will provide additional insights regarding long-term vaccine effectivity and COVID-19 immunity by sex.