Abstract
The long-term association between mRNA-based Coronavirus Disease 2019 (COVID-19) vaccination and the development of autoimmune connective tissue diseases (AI-CTDs) remains unclear. In this nationwide population-based cohort study involving 9,258,803 individuals, we investigated the incidence of AI-CTDs associated with mRNA vaccines for ≥1 year and further analysed the risk by stratifying by sex, age, mRNA vaccine type, COVID-19 diagnosis, cross-vaccination with a non-mRNA vaccine, and booster vaccination. The risk of developing most AI-CTDs did not increase following mRNA vaccination. However, systemic lupus erythematosus and bullous pemphigoid were significantly more prevalent in vaccinated individuals than in controls. Comparable results were reported in the subgroup analyses, especially in the subgroups comprising women or patients aged ≥40 years who showed a higher risk of developing bullous pemphigoid following mRNA vaccination. Our results suggest that mRNA-based COVID-19 vaccinations are not associated with a high incidence of most AI-CTDs. However, further research is needed regarding its potential association with certain conditions including systemic lupus erythematosus and bullous pemphigoid.