COVID-19 vaccine reactogenicity among participants enrolled in the GENCOV study

Background GENCOV is a prospective, observational cohort study of COVID-19-positive adults. Here, we characterize and compare side effects between COVID-19 vaccines and determine whether reactogenicity is exacerbated by prior SARS-CoV-2 infection. Methods Participants were recruited across Ontario, Canada. Participant-reported demographic and COVID-19 vaccination data were collected using a questionnaire. Multivariable logistic regression was performed to assess whether vaccine manufacturer, type, and previous SARS-CoV-2 infection are associated with reactogenicity. Results Responses were obtained from n = 554 participants. Tiredness and localized side effects were the most common reactions across vaccine doses. For most participants, side effects occurred and subsided within 1–2 days. Recipients of Moderna mRNA and AstraZeneca vector vaccines reported reactions more frequently compared to recipients of a Pfizer-BioNTech mRNA vaccine. Previous SARS-CoV-2 infection was independently associated with developing side effects. Conclusions We provide evidence of relatively mild and short-lived reactions reported by participants who have received approved COVID-19 vaccines.