COVID-19 infection and hospitalization 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.