Understanding variables that influence antibody responses to SARS-CoV-2 vaccination within a population can provide valuable information on future vaccination strategies. In this study, I examined the antibody responses to SARS-CoV-2 vaccination in Manitoba, Canada using serum specimens collected by Cadham Provincial Laboratory between March 2020 and March 2023. Specimens were tested for spike and nucleocapsid IgG against SARS-CoV-2 using clinically validated assays. I assessed the impacts of multiple factors on post-vaccination antibody titres including type of vaccine, age, sex, geographic location, number of doses received, timing of vaccination, and influence of previous infections. My investigation demonstrated that vaccination with one dose of Moderna mRNA-1273 elicited higher anti-spike IgG titres overall compared to Pfizer BNT162b2 vaccination, while one dose of Pfizer BNT162b2 followed by a second dose of Moderna mRNA-1273 exhibited higher titres than two doses of Pfizer BNT162b2 or Moderna mRNA-1273, irrespective of age. Age had the greatest effects on antibody responses, with older age groups exhibiting consistently lower anti-spike IgG titres of than younger ages. Antibody titres did not appear to be affected by sex or geographic location. My results identify how factors such as age and type of vaccine can influence antibody responses to vaccination. This information highlights the importance of tailoring vaccine regimens to those at increased risk of severe COVID-19 and can be used to inform future vaccination strategies, scheduling of booster doses and public health measures.February 202
