Turning the Tide against Herpes Zoster in Rheumatoid Arthritis Patients Treated with JAK Inhibitors.

: This study aimed to evaluate the incidence of Herpes Zoster (HZ) in patients with rheumatoid arthritis (RA) treated with Janus kinase inhibitors (JAKi), and to predict potential risk factors for HZ development. : We retrospectively analysed medical records from RA patients at our rheumatology unit who met the 2010 ACR/EULAR criteria for RA and were receiving JAKi. The incidence and course of HZ were assessed through chart review and supplementary phone interviews. : A total of 198 JAKi-treated patients were monitored for an average of 18.5 months. Nine subjects experienced HZ, resulting in an incidence of 2.95 per 100 patient-years. No demographic or treatment-related differences were found among patients who developed HZ and those who did not. Disease duration (OR: 1.06, 95% CI: 1.01-1.12), time on JAKi treatment (OR: 1.04, 95% CI: 1.009-1.073), higher disease activity at JAKi initiation (OR: 4.16, 95% CI: 1.07-16.17), and at 3-month follow-up (OR: 6.0, 95% CI: 1.35-26.60) were identified as predictors of HZ occurrence. Thirty-six patients received vaccination against HZ, and none reported adverse reactions or flare-ups during a mean follow-up of 9.6 months. : The incidence of HZ aligns with published data, suggesting that disease and treatment duration, as well as disease activity, are significant predictors of HZ in RA patients on JAKi therapy. Vaccination against HZ proved to be safe and effective, underscoring its potential protective value in this patient population.