Immunogenicity of the Varicella-Zoster Vaccine in Community-Dwelling Non-robust Elderly Individuals Compared to Robust Elderly Individuals: A Prospective Cohort Study

To determine whether immunogenicity of the herpes zoster live-attenuated vaccine (ZVL) in elderly individuals is influenced by frailty status and cytokine levels, individuals aged at least 65 years were prospectively administered ZVL after their frailty status and cytokine levels were assessed. Humoral and cellular immunogenicity were assessed using enzyme-linked immunosorbent assays for the varicella-zoster virus–specific IgG antibody and varicella-zoster virus–specific enzyme-linked immunospot assays, before and 6 weeks after vaccination. We enrolled 69 participants (mean age, 74.3 years); 31 were non-robust. Thirty-seven participants had a greater than 2 geometric mean fold rise in IgG antibodies, 22 more participants had at least 10 spot-forming cells/106 peripheral blood mononuclear cells (from 35 to 57 participants), and 42 experienced a twofold geometric mean fold rise increase of spot-forming cells 6 weeks after vaccination. The geometric mean fold rises of the antibody titers were similar in the robust and non-robust groups; moreover, the baseline enzyme-linked immunospot assay geometric mean values were not significantly different before or 6 weeks after vaccination. We observed no significant correlations between baseline cytokine levels and immunogenicity. Approximately half of the community-dwelling elderly participants in this study experienced a twofold rise in antibodies and one-third more participants showed at least 10 spot-forming cells after ZVL administration, suggesting that the ZVL can boost immunity in non-robust (especially pre-frail) and robust elderly individuals.