Recombinant Zoster Vaccine Is Efficacious and Safe in Frail Individuals

Abstract

BACKGROUND/OBJECTIVES Frail participants are often under‐represented in randomized trials, raising questions about outcomes of interventions in real‐world settings. Frailty is strongly associated with vulnerability to illness and adverse health outcomes. We studied the impact of frailty on recombinant zoster vaccine (RZV) clinical outcomes. DESIGN/SETTING Data from two previously conducted phase III randomized trials of RZV were pooled. These two parent trials were conducted concurrently at the same study sites using the same methods. PARTICIPANTS/INTERVENTION In the two parent studies, participants aged ≥50 years (ZOE‐50 study) and ≥70 years (ZOE‐70 study), respectively, were randomized 1:1 to receive two doses of RZV or placebo. MEASUREMENTS In the current ZOE‐Frailty study (NCT03563183), a frailty index was created using previously validated methods. Clinical outcomes assessed by frailty status included vaccine efficacy, immunogenicity, reactogenicity, and safety. RESULTS Of 29,305 participants from the pooled ZOE‐50 and ZOE‐70 total vaccinated cohort, 92% were included in this study. Mean age was 68.8 years; 58.1% were women; 45.6% were pre‐frail and 11.3% frail. The percentage of frail participants increased with age from 5.7% aged 50–59 years to 22.7% aged ≥80 years. RZV vaccine efficacy against herpes zoster was >90% for all frailty subgroups (non‐frail: 95.8% (95% confidence interval = 91.6–98.2), pre‐frail: 90.4% (84.4–94.4), frail: 90.2% (75.4–97.0)). The RZV group demonstrated robust anti‐gE antibody and gE‐specific CD4²⁺ responses, with mean concentrations remaining above pre‐vaccination levels at least 3 years post‐dose two, in all frailty subgroups. In the RZV group, the percentage of participants reporting solicited adverse events tended to decrease with increasing frailty. CONCLUSION The relatively nonrestrictive inclusion/exclusion criteria in the parent ZOE studies resulted in a range of participants that included frail and pre‐frail older adults. RZV significantly reduced the risk of herpes zoster across all frailty subgroups.