Prospective assessment of reactogenicity and disease activity after recombinant zoster vaccination in Japanese patients with inflammatory bowel disease

Introduction Patients with inflammatory bowel disease (IBD) are at increased risk of herpes zoster, particularly in the era of advanced therapies. However, prospective safety data on recombinant zoster vaccine (RZV) in Asian patients with IBD remain limited. This study prospectively evaluated the safety, reactogenicity, and short-term changes in disease activity after RZV administration in Japanese patients with IBD. Methods This prospective observational study included adults with IBD who received RZV in routine clinical practice at two tertiary centers in Japan between October 2023 and March 2025. Adverse events were prospectively recorded using patient diaries. Solicited adverse events were predefined local and systemic events occurring within 7 days after vaccination. Unsolicited adverse events were defined as the same events occurring after day 7 or any other adverse events occurring within 30 days. Serious adverse events were assessed for 6 months after the second dose. In patients with ulcerative colitis (UC), disease activity was longitudinally assessed using the two-item patient-reported outcome (PRO2). Results Forty-eight patients with IBD, including 44 with UC and four with Crohn's disease, completed the two-dose RZV series. At least one solicited adverse event occurred in all patients, whereas no serious adverse events were observed. No patient required treatment escalation, an unscheduled medical visit, or hospitalization, and no patient was judged to have a clinical flare. In patients with UC, longitudinal PRO2 assessment showed no apparent worsening during the 8 weeks after vaccination. Conclusion In this prospective Japanese cohort comprising predominantly patients with UC, RZV was associated with frequent but non-serious reactogenicity and no clear signal for short-term clinical flare. Because only four patients with CD were included, these findings primarily apply to patients with UC and do not permit firm conclusions regarding patients with CD.