Incidence of Herpes Zoster in Patients With Rheumatoid Arthritis: Comparison With Controls and Risk According to Different Treatments

Objective: To compare the incidence of herpes zoster (HZ) between patients with rheumatoid arthritis (RA) and matched controls from a health plan in Buenos Aires, and to assess incidence under different immunosuppressive treatments. Methods: Patients with newly diagnosed RA between 2000 and 2023 were matched 1:2 by age and sex with controls. Incidence densities per 100 patient-years (PY) were calculated. Cox regression and Kaplan-Meier analyses were performed to identify factors associated with HZ. Results: A total of 460 RA patients and 920 controls (81.3% women, mean age: 62.2 y) were included, with a median follow-up of 9 years. The RA cohort contributed 4184 PY and controls 9783 PY. Forty-six HZ events occurred in RA and 29 in controls. HZ incidence was 1.08 (95% CI: 0.80-1.47) per 100 PY in RA versus 0.29 (95% CI: 0.19-0.44) in controls [incidence rate ratio (IRR) 3.63; 95% CI: 2.28-5.77; p <0.001]. Compared with conventional DMARDs, biologic therapy increased risk (IRR: 2.48; p =0.023), and JAK inhibitors further elevated it (IRR: 4.47; p =0.001). In multivariate analysis, older age (HR: 1.04; p =0.005) and biologic use (HR: 2.39; p =0.006) were independent predictors. Most HZ cases involved one dermatome; 9.3% were disseminated, and 6.8% required hospitalization. Postherpetic neuralgia was more frequent in RA (42.2% vs. 7.7%; p =0.002). Conclusion: HZ incidence was over 3-fold higher in RA patients, particularly among those treated with biologics and JAK inhibitors.