Final analysis of the ZOE-LTFU trial to 11 years post-vaccination: efficacy of the adjuvanted recombinant zoster vaccine against herpes zoster and related complications

Background: Herpes zoster (HZ) vaccines should provide durable protection against HZ and HZ-related complications. We report the final analysis of a long-term follow-up (LTFU) study (ZOE-LTFU) including 11 years of follow-up after primary vaccination with recombinant zoster vaccine (RZV). Methods: ZOE-LTFU (NCT02723773) was an open-label, phase 3b study following participants of two phase 3 trials, ZOE-50 and ZOE-70. ZOE-LTFU started approximately 5 years post-vaccination in ZOE-50/70 and participants were followed for 6 years. The primary objective was to assess vaccine efficacy (VE) against HZ during ZOE-LTFU. Secondary objectives included VE against HZ from 1 month post-dose 2 in ZOE-50/70 until end of ZOE-LTFU, VE against post-herpetic neuralgia (PHN) and non-PHN complications, immunogenicity, and long-term safety. The VE calculation used a historical control constructed with ZOE-50/70 placebo data. Findings: VE was assessed in the modified total vaccinated cohort (n = 7273 [mean age 67·3 years at first vaccination]). During ZOE-LTFU, VE was 79·8% (95% confidence interval [CI]: 73·7, 84·6) and 73·2% (95% CI: 62·9, 80·9) against HZ in participants ≥50 and ≥70 years at first vaccination, respectively, and was 87·5% (95% CI: 64·8, 96·8) against PHN and 91·7% (95% CI: 43·7, 99·8) against other HZ-related complications in participants ≥50 years. From 1 month post-dose 2 in ZOE-50/70 to the end of ZOE-LTFU, VE against HZ was 87·7% (95% CI: 84·9, 90·1) in participants ≥50 years and sustained at 82·0% (95% CI: 63·0, 92·2) in the eleventh year post-vaccination. Humoural and cell-mediated immune responses plateaued at over 5-fold and ∼7-fold, respectively, above pre-vaccination levels in ZOE-50/70. No RZV-related serious adverse events occurred. Interpretation: Efficacy of RZV against HZ and associated complications remained high through 11 years post-vaccination, indicating sustained clinical benefit. Funding: The funder of the study was GSK who was involved in study design, data collection, data analysis, data interpretation, writing of the report, and the decision to submit for publication.