Persistence of Immune Response to an Adjuvanted Varicella‐Zoster Virus Subunit Candidate Vaccine for up to Year 9 in Older Adults

BACKGROUND: In the ZOE-50 and ZOE-70 clinical trials, the candidate herpes-zoster subunit vaccine (HZ/su; 50µg varicella-zoster virus glycoprotein E [gE] and AS01(B) Adjuvant System) demonstrated high efficacy against HZ, with limited waning over 4 years and consistent efficacy across age cohorts. In adults ≥60 years of age, the immune responses elicited by 2 HZ/su doses administered 2 months apart persisted for at least 6 years.(1) Here we report immunogenicity and safety 9 years post-initial vaccination. METHODS: This Phase IIIB, open, long-term extension study (NCT02735915) followed 70 participants who received 2 HZ/su doses in the initial trial (NCT00434577). Blood samples to evaluate the persistence of cellular (intracellular cytokine staining) and humoral (ELISA) immune responses were taken at 9 years post-initial vaccination. Limited safety follow-up was performed (1 visit). RESULTS: All 70 participants (mean age at dose 1: 72.3 years; 61.4% female) were included in the according-to-protocol analysis. The fold increases over pre-vaccination in the frequency of gE-specific CD4+ T-cells expressing ≥2 activation markers plateaued after 4 years post-dose 1 (year 4: 3.4, year 5: 3.0, year 6: 3.4, year 9: 3.4). Anti-gE antibody geometric mean concentrations were also stable from year 4 onwards (Table 1) and remained above the pre-vaccination value of 1213.1mIU/mL. Cellular and humoral responses at year 9 were similar across age strata (60–69, ≥70 years). No vaccine-related serious adverse events nor suspected HZ episodes were reported. CONCLUSION: In adults ≥60 years of age, HZ/su-induced cellular and humoral immune responses remained above pre-vaccination levels for at least 9 years post-initial vaccination, confirming immune persistence predictions(2) based on 6-year data. DISCLOSURES: S. Volpe, GSK: Employee, Salary; T. F. Schwarz, GSK: Investigator and Scientific Advisor, Consulting fee; J. Smetana, GSK: Investigator, personal fees; S. Ravault, GSK: Employee, GSK shares and Salary; M. P. David, GSK: Employee, Salary and stock; A. Bastidas, GSK: Employee, Salary; L. Oostvogels, GSK: Employee and Shareholder, Salary and shares