Prevalence and Risk Factors of COVID-19 Reinfection in Patients with Rheumatoid Arthritis: A Retrospective Observational Study.

Purpose: To identify the prevalence and risk factors of coronavirus disease 2019 (COVID-19) reinfection in patients with rheumatoid arthritis (RA).

Materials and methods: This study retrospectively analyzed patients with RA with a documented COVID-19 infection between January 2021 and December 2022 at a tertiary hospital in Seoul, South Korea. Reinfection was defined as a subsequent positive test result for severe acute respiratory syndrome coronavirus 2 at least 3 months after the initial infection. Cox proportional hazards models with backward elimination were employed to assess the association between potential risk factors and risk of reinfection.

Results: Of 351 included patients with RA {female, 81.5%; median age, 58.0 years [interquartile range (IQR), 48.0-66.0]}, 252 (71.8%) were treated with methotrexate and 12 (3.4%) received leflunomide during the initial infection. Over a median follow-up of 1.5 (IQR, 1.1-1.6) years, 43 (12.3%) patients experienced reinfection, equating to an incidence rate of 8.97 per 100 patient-years. The median time interval between infections was 0.8 (IQR, 0.6-1.2) years. Among the risk factors, leflunomide use showed a significant association with reinfection (hazard ratio, 2.968; 95% confidence interval, 1.057-8.335; p=0.039). However, no significant changes occurred in disease activity following reinfection [disease activity score using 28 joints: baseline median, 2.3 (IQR, 1.9-2.8); post-reinfection median, 2.3 (IQR, 1.8-2.6), p for change=0.895].

Conclusion: In this retrospective cohort study of patients with RA with COVID-19 infection, approximately 12% of patients experienced reinfection without significant change in disease activity. Leflunomide use was associated with a higher risk of reinfection.