Real-world effectiveness of recombinant herpes zoster vaccine: A retrospective, cohort study in Japan

Background: In Japan, a two-dose, recombinant herpes zoster vaccine (RZV) has been available since 2020, but vaccination coverage is low because vaccination is voluntary. This study investigated the real-world effectiveness of the RZV for preventing herpes zoster (HZ) by using clinical databases. Methods: A retrospective, cohort study was conducted by using databases created at a dermatology clinic in Miyazaki Prefecture, Japan. Vaccinated patients were extracted from the Shingrix Database, and corresponding unvaccinated patients were selected from the Outpatients Database, with individuals matched by sex, age (5-year intervals), and the outpatient visit date (±3 months from the vaccination date of the vaccinated patient). Cases of HZ as a study outcome were identified by the HZ Database until August 2024. For analysis, a conditional logistic regression model was used to calculate the odds ratio (OR) and 95% confidence interval (CI), and vaccine effectiveness was calculated as (1 - OR) × 100 (%). Results: Between 2020 and 2023, 612 patients received the RZV, and 612 corresponding unvaccinated patients were extracted from the Outpatients Database. Of them, 2 vaccinated patients (0.3%) and 13 unvaccinated patients (2%) developed HZ from the date of the vaccination/outpatient visit until August 2024 (P<0.01). The adjusted OR (95% CI) of vaccination for HZ infection was 0.16 (0.04-0.69), giving a vaccine effectiveness of 84%. Effectiveness was the same, regardless of age. Conclusion: The RZV provides high effectiveness for preventing HZ in the clinical setting. The necessity or the timing of booster vaccination warrants further investigation.