Effectiveness of the Recombinant Zoster Vaccine in Adult Patients with Multiple Sclerosis: A Claims-Based Retrospective Cohort Study in the United States.

OBJECTIVES:To assess vaccine effectiveness (VE) of the recombinant zoster vaccine (RZV) in adults with multiple sclerosis (MS). METHODS:This retrospective study included adults aged ⩾18 years with MS insured by Medicare or one of seven United States (US) commercial health insurers from January 2018 to September 2023. Adults receiving two RZV doses ⩾28 days apart were matched with four or less unvaccinated comparators on insurer, sex, and age. Adjusted hazard ratios (HRs) of incident herpes zoster (HZ) ⩾ 31 days after the second RZV dose were estimated using Cox models with inverse probability of treatment weighting applied to the matched cohorts to balance potential confounders. VE was calculated as (1 - HR) × 100. RESULTS:The Medicare cohort included 8705 vaccinated and 34,407 unvaccinated patients; the commercially insured cohort included 6025 vaccinated and 22,685 unvaccinated patients. Most patients in both cohorts were aged ⩾50 years. Crude HZ incidence in unvaccinated patients was 13.7 and 12.7/1000 person-years in the Medicare and commercially insured cohorts, while crude incidence among vaccinated patients was 4.6 and 2.4/1000 person-years. Weighted analyses demonstrated VE of 64% (95% confidence interval [CI]: 51%-74%) in Medicare and 81% (95% CI: 70%-88%) in commercially insured patients. CONCLUSION:RZV demonstrated robust VE, preventing 64%-81% of HZ cases in this MS population predominantly aged 50 years or older.