Preventive Effectiveness of Recombinant Zoster Vaccine in Rheumatoid Arthritis Patients Treated with Janus Kinase Inhibitors.

Objective This study assessed the effectiveness of the recombinant zoster vaccine (RZV) in preventing herpes zoster (HZ) in rheumatoid arthritis (RA) patients treated with Janus kinase (JAK) inhibitors. Methods This was a retrospective analysis. The patients were categorized into vaccinated (n=74) and unvaccinated (n=120) groups. HZ incidence was compared using the Kaplan-Meier method, and vaccine effectiveness was estimated using inverse probability of treatment weighting (IPTW) to adjust for baseline confounding factors. Patients 194 Japanese RA patients were analyzed treated with JAK inhibitors at our institution from January 2020 to September 2024. Results The observation spanned 124.4 person-years in the vaccinated group and 256.2 in the unvaccinated group. HZ occurred in six vaccinated cases (4.8 per 100 person-years) versus 20 unvaccinated cases (7.8 per 100 person-years) (p=0.32). The overall efficacy of the vaccine was 59.1%. HZ incidence varied by JAK inhibitor: baricitinib (5.5 vs 9.9), upadacitinib (12.4 vs 6.2), and filgotinib (0.0 vs 1.6) per 100 person-years. Vaccinated patients who developed HZ had significantly lower lymphocyte counts and higher SDAI and CDAI scores. Conclusion Although not statistically significant, RZV vaccination tended to reduce the incidence of HZ in Japanese RA patients receiving JAK inhibitors. The effectiveness varied according to the type of JAK inhibitor, with lower lymphocyte counts and higher disease activity, and it may predict insufficient protection.