The STOP-HZ study aims to determine the optimal timing for herpes zoster vaccination in rheumatoid arthritis patients starting JAK inhibitor therapy. The study, expected to run from September 2023 through August 2025, is evaluating immune response to the recombinant zoster vaccine (RZV) when administered concurrently with, or 8 weeks before, initiating tofacitinib treatment.

The primary endpoint will measure VZV-specific IgG antibody titers at week 12 compared to baseline, with secondary endpoints including VZV-specific T-cell response, changes in rheumatoid arthritis disease activity, and adverse events. The trial will divide participants into two groups, both receiving RZV on day 1 and week 8.