RESUMEN
INTRODUCTION: Adverse events (AE) such as pain at injection site or fever are common after COVID-19 vaccination. We aimed to describe determinants of AE after COVID-19 vaccination and investigate the association between AE and pre- and post-vaccination antibody concentrations. METHODS: Participants of an ongoing prospective cohort study (VASCO) completed a questionnaire on AE within two months after COVID-19 vaccination and provided 6-monthly serum samples. Data from May 2021 to November 2022 were included. Logistic regression analyses were performed to investigate determinants of AE after mRNA vaccination, including pre-vaccination Ig antibody concentrations against the receptor binding domain. Multivariable linear regression was performed in SARS-CoV-2 naive participants to assess the association between AE and log-transformed antibody concentrations 3-8 weeks after mRNA vaccination. RESULTS: 47,947 AE questionnaires were completed by 28,032 participants. In 42% and 34% of questionnaires, injection site and systemic AE were reported, respectively. In 2.2% of questionnaires, participants sought medical attention due to AE. AE were reported significantly more frequently by women, younger participants (<60 years), participants with medical risk conditions and Spikevax recipients (versus Comirnaty). Higher pre-vaccination antibody concentrations were associated with higher incidence of systemic AE after the second and third dose, but not with injection site AE or AE for which medical attention was sought. Any AE after the third dose was associated with higher post-vaccination antibody concentrations (geometric mean concentration ratio: 1.38, 95%CI 1.23-1.54). CONCLUSION: Our study suggests that high pre-vaccination antibody levels induce AE, and that experiencing AE may be a marker for a good antibody response to vaccination.