The Adjuvanted Recombinant Zoster Vaccine Confers Long-term Protection Against Herpes Zoster: Interim Results of an Extension Study of the Pivotal Phase III Clinical Trials (ZOE-50 and ZOE-70).

Background This is an ongoing follow-up study (NCT02723773) evaluating persistence of efficacy and immune responses for six additional years in adults vaccinated with the glycoprotein E (gE)-based adjuvanted recombinant zoster vaccine (RZV) at ≥50 years of age in two pivotal efficacy trials (ZOE-50/70). The present interim analysis was performed after ≥2 additional years of follow-up (between 5.1 and 7.1 years [mean] post-vaccination) and includes partial data for year (Y)8 post-vaccination. Methods Annual assessments were performed for efficacy against herpes zoster (HZ) from Y6 post-vaccination onwards, and for anti-gE antibody concentrations and gE-specific CD4[2+] T-cell (expressing ≥2 of four assessed activation markers) frequencies from Y5 post-vaccination onwards. Results Of 7413 participants enrolled for the long-term efficacy assessment, 7277 (mean age at vaccination: 67.2 years), 813, and 108 were included in the cohorts for the evaluation of efficacy, humoral immune responses, and cell-mediated immune responses, respectively. Efficacy of RZV against HZ through this interim analysis was 84.0% (95% confidence interval [CI]: 75.9-89.8) from the start of this follow-up study and 90.9% (95%CI: 88.2-93.2) from vaccination in ZOE-50/70. Annual vaccine efficacy estimates were >84% for each year since vaccination and remained stable during this follow-up study through the interim analysis. Anti-gE antibody geometric mean concentrations and median frequencies of gE-specific CD4[2+] T cells had plateaued throughout this follow-up study up to the interim analysis, at ~6-fold above pre-vaccination levels. Conclusion Efficacy against HZ and immune responses to RZV remained high, suggesting that the clinical benefit of RZV in older adults is sustained for at least seven years post-vaccination.