Objective: To determine how serologic responses to COVID vaccination/infection in immunemediated inflammatory disease (IMID) are affected by time since last vaccination and other factors.
Methods: Post-COVID-19 vaccination, data and dried blood spots/sera were collected from adults with rheumatoid arthritis, inflammatory bowel disease, systemic lupus, ankylosing spondylitis/spondylarthritis and psoriasis/psoriatic arthritis. First sample was at enrolment and then 2-4 weeks and 3, 6, and 12 months after latest vaccine dose. Multivariate generalized estimating equation regressions (including medications, demographics, and vaccination history) evaluated serologic response, based on log-transformed anti-RBD IgG titres; we also measured anti-nucleocapsid IgG.
Results: Positive associations for log-transformed anti-RBD titres were seen with female sex, number of doses, and self-reported COVID infections in 2021-2023. Negative associations were seen with prednisone, anti-TNF agents, and rituximab.Over 2021-2023, most (94%) of anti-nucleocapsid positivity was associated with a self-reported infection in the 3 months prior. From March 2021 to Feb 2022, anti-nucleocapsid positivity was present in 5-15% of samples and was highest in the post-Omicron era, with anti-nucleocapsid positivity trending to 30-35% or higher as of March 2023. Anti-nucleocapsid positivity in IMID remained lower than Canada's general population seroprevalence (>50% in 2022 and >75% in 2023).Time since last vaccination was negatively associated with log-transformed anti-RBD titres, particularly after 210 days.
Conclusion: Ours is the first pan-Canadian IMID assessment of how vaccine history and other factors affect serologic COVID-19 vaccine responses. These findings may help individuals personalize vaccination decisions, including consideration of additional vaccination when >6 months has elapsed since last COVID vaccination/infection.