Comparator-Dependent Safety Signals for Incident Systemic Autoimmune Rheumatic Diseases After mRNA COVID-19 Vaccination: A Systematic Review

Background: Pharmacovigilance systems have flagged possible associations between mRNA COVID-19 vaccination and systemic autoimmune inflammatory rheumatic diseases (AIRDs), generating uncertainty for rheumatologists counselling patients. As the first population-scale deployment of an mRNA vaccine platform, COVID-19 vaccination provides a unique setting to examine whether autoimmune safety signals detected in spontaneous reporting systems correspond to measurable disease risk. We synthesised pharmacovigilance and population-based evidence on incident EULAR-defined systemic AIRDs after mRNA COVID-19 vaccination and assessed whether disproportionality signals were corroborated by analytical studies. Methods: We conducted a PRISMA 2020-compliant systematic review searching MEDLINE, Web of Science, Scopus, Embase, and the Cochrane Library from 2019 to April 2026, supplemented by medRxiv and trial registries. Eligible studies included pharmacovigilance disproportionality analyses and analytical studies, including cohorts and randomised controlled trials, evaluating BNT162b2 or mRNA-1273 in adults without known pre-existing autoimmune disease. Risk of bias was assessed using READUS-PV, ROBINS-I, and RoB 2. Meta-analysis was not performed because of substantial heterogeneity. Results: Fourteen studies were included: seven pharmacovigilance studies and seven analytical studies. Disproportionality analyses suggested increased reporting of selected AIRDs, most consistently polymyalgia rheumatica and giant cell arteritis, mainly when all other adverse-event reports served as comparators. These signals were largely neutral when influenza vaccines were the reference. Across analytical studies, associations were inconsistent; modest increases in systemic lupus erythematosus appeared only in selected analyses. Long-term evidence was scarce: only four studies, from three countries (South Korea, Israel, and Norway), followed participants for up to approximately one year, and three of these reported at least one positive association—systemic lupus erythematosus, post-booster rheumatoid arthritis, and polymyalgia rheumatica in older adults—whereas studies restricted to risk windows of three months or less reported no increase. Conclusions: The available evidence does not indicate a consistent increase in incident systemic AIRDs after mRNA COVID-19 vaccination. Although pharmacovigilance studies identified comparator-dependent signals for selected diseases, particularly polymyalgia rheumatica and giant cell arteritis, these findings were generally not confirmed in comparative population-based studies and should be considered hypothesis-generating. Delayed-onset disease remains poorly characterised, and studies with at least one year of follow-up are needed.