Herpes Zoster Frequency and Adjuvanted Recombinant Zoster Vaccination after Allogeneic Hematopoietic Cell...

The prevention of herpes zoster (HZ) is of prime importance in patients undergoing allogeneic hematopoietic cell transplantation (alloHCT). Shingrix, an inactivated, adjuvanted recombinant zoster vaccine (aRZV), is now available and recommended for preventing HZ in seropositive immunocompromised patients. The safety and efficacy of this vaccine have been established in autologous HCT (autoHCT) recipients and other immunocompromised patients; however, data on alloHCT recipients are limited. The primary outcome of this study was a comparison of HZ frequency in alloHCT recipients who received aRZV vaccination and those who did not. Other characteristics of interest include the clinical presentation of HZ, treatment, and outcomes related to the HZ episode. This single-center retrospective observational cohort study was conducted at Princess Margaret Hospital, Toronto, Canada between April 1, 2018, and May 1, 2024. Adult patients who underwent alloHCT between April 1 2018, and December 31, 2022, were included in a prospective registry. Follow-up was censored at time of death, at 90 days after the first episode of HZ, at loss to follow-up, at the end of the study period, or 36 months post-alloHCT. Data were collected systematically from the electronic medical record or registry. A confirmed HZ episode was defined by clinical and/or molecular criteria. Statistical analysis was performed to determine risk factors associated with HZ and the relative risk (RR) of HZ episodes occurring in those ≥12 months post-alloHCT considering aRZV status and the cumulative follow-up period. A total of 445 patients were included. The median age was 56 years (interquartile range [IQR], 38 to 64 years), with a slight male predominance (n = 241/445; 54.2%). From ≥12 months post-alloHCT, there were 43 HZ episodes, including 26 of 263 patients (9.9%) who had received at least 1 dose of aRZV, 19 of 263 (7.2%) who had received 2 doses, 7 of 70 (10.0%) who did not receive RZV, and 10 of 112 (8.9%) with unknown vaccination status. The median time to HZ after receipt of any dose of aRZV was 8.1 months (IQR, 3.9 to 12.3 months). Overall, the median time to first HZ episode post-alloHCT was 20.7 months (IQR, 16.9 to 27.9 months), and the majority of HZ episodes occurred after cessation of antiviral prophylaxis (n = 38 of 43; 88.4%). Most HZ episodes were localized (n = 38; 88.4%) and treated in the outpatient setting with oral antiviral therapy (n = 39; 90.7%) for a median of 10 days (IQR, 7 to 14 days). Disseminated HZ did not occur in any aRZV recipients. Considering aRZV status and follow-up period, the RR of HZ in those who had received 2 doses of aRZV compared to those who had not received any doses of aRZV was 0.90 (95% confidence interval, 0.75 to 1.07; P = .22). In a sensitivity analysis, the risk of HZ was reduced (lower RR) in those receiving aRZV ≥12 months post-alloHCT compared with those who did not receive aRZV. Overall, the receipt of aRZV did not appear to influence the frequency of HZ in patients post-alloHCT; however, there may be disease severity modification and benefit if received beyond 12 months post-HCT. We provide preliminary findings that would benefit from further evaluation in a prospective, randomized trial.