Clinical Effectiveness of the Recombinant Zoster Vaccine for Preventing Herpes Zoster in Individuals With Kidney Transplants: A Retrospective Cohort Study

BACKGROUND: People who have received kidney transplants (KTs) are at increased risk for herpes zoster (HZ). The recombinant zoster vaccine (RZV) is recommended for immunocompromised individuals based on immunogenicity data, including studies in solid organ transplant populations. However, evidence on its real-world effectiveness in transplant recipients remains limited. In South Korea, RZV became available in March 2023, providing an opportunity to assess the association between RZV vaccination and incident HZ among individuals who received KT in a retrospective cohort study. METHODS: We included all adults (≥ 18 years) who underwent KT at a single 2700-bed tertiary center in Seoul, South Korea, from January 2020 through December 2024. Vaccination status was treated as a time-varying exposure. Incidence rates and adjusted hazard ratios (aHRs) were estimated using time-dependent Cox regression. RESULTS: Among 1761 adults who received KT, 388 individuals received the RZV, while 1373 remained unvaccinated. During follow-up, HZ occurred in 78 unvaccinated individuals (5.7%), while no cases occurred in the vaccinated group over 398.3 person-years. The incidence rate of HZ was 16.4 per 1000 person-years (95% confidence interval [CI]: 13.0-20.5) in the unvaccinated group and 0 (95% CI: 0.0-9.3) in the vaccinated group. In a time-dependent Cox model with Firth penalization, RZV was associated with a lower hazard of HZ (aHR, 0.06; 95% CI: 0.00-0.43; p < 0.001). CONCLUSION: No HZ events occurred among vaccinated individuals in this cohort, a finding consistent with a protective association of RZV after KT. These findings support current recommendations for RZV use in immunocompromised populations.