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

Abstract

Background. In the ZOE-50 and ZOE-70 clinical trials, the candidate herpes-zoster subunit vaccine (HZ/su; 50μ g varicella-zoster virus glycoprotein E [gE] and AS01B Adjuvant System) demonstrated high effcacy against HZ, with limited waning over 4 years and consistent effcacy 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-vaccina-tion in the frequency of gE-specifc CD4+ T-cells expressing ≥2 activation markers plateaued After 4 years post-dose1 (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 of1213.1mIU/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 Presented].