To further elucidate the effects of rare systemic autoimmune rheumatic diseases (SARD) and their treatment on antibody development after vaccination against SARS-CoV-2, we compared patients with and without immunosuppressive therapy to healthy controls in an observational cohort study.

We enrolled 52 patients with SARD and 72 healthy subjects in a prospective, observational study at the Medical University of Vienna and measured the humoral response 6 months after two mRNA vaccinations and 2–6 weeks after a third dose.

Patients with vasculitis showed significantly (p=0.02) lower antibody titres 6 months after vaccination (median 247 BAU/mL, IQR [185–437]), as compared with healthy controls (median 514 BAU/mL, [185–437], IQR 323; 928, vasculitis patients: 247, IQR [185; 437], p

Patients with SARD displayed lower antibody development after booster vaccination, even if antibody levels after two immunisations were comparable to healthy controls. Our data may be limited due to sample size, but it provides pointers for a more individualised, antibody-titre-oriented approach and earlier booster vaccination in patients with SARD.