COVID-19 infection and hospitalisation risk according to vaccination status and DMARD treatment in patients with rheumatoid arthritis

Objectives: The objectives of this study were to investigate the incidence of COVID-19 hospitalization in unvaccinated and vaccinated patients with RA compared with matched controls, and in patients with RA according to DMARD treatment.Methods: This was a Danish nationwide matched-cohort study from January to October 2021. Patients with RA were identified in the DANBIO register and matched 1:20 with individuals from the general population on age, sex, and vaccination status. Primary and secondary outcomes were COVID-19 hospitalization (Danish National Patient Register) and first-time positive SARS-CoV-2 PCR test (Danish COVID-19 Surveillance Register), respectively. Stratified by vaccination status, incidence rates (IRs) per 1000 person years (PYs) and comorbidity-adjusted hazard ratios (aHRs) in cause-specific Cox models were calculated with 95% confidence intervals.Results: In total, 28 447 unvaccinated patients and 568 940 comparators had IRs for COVID-19 hospitalization of 10.4 (8.0–13.4) and 4.7 (4.3–5.1) per 1000 PYs, respectively (aHR 1.88, 1.44–2.46). When fully vaccinated, corresponding IRs were 0.9 (0.5–1.6) and 0.5 (0.4–0.6) per 1000 PYs (aHR 1.94, 1.03–3.66). Unvaccinated RA patients had an aHR of 1.22 (1.09–1.57) for testing positive for SARS-CoV-2 and 1.09 (0.92–1.14) among vaccinated RA patients. Vaccinated rituximab-treated patients had increased crude IR of COVID-19 hospitalization compared with conventional DMARD–treated patients.Conclusion: The incidence of COVID-19 hospitalization was increased for both unvaccinated and vaccinated patients with RA compared with controls. Importantly, the parallel decreasing risk for patients with RA suggests a comparable relative benefit of vaccination in most patients.