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Abstract 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 AS01B 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 predictions2 based on 6-year data. Table 1 Pre-vaccination (95% CI) Year 4 (95% CI) Year 5 (95% CI) Year 6 (95% CI) Year 9 (95% CI) Anti-gE antibody GMC (mlU/mL) 1213.1 (983.8–1495.9) 9643.5 (8309.7–11191.3) 9124.1 (7805.1–10666.0) 8490.5 (7292.1–9885.7) 8931.2 (7625.7–10460.3) 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