Chan, C.C.Y., et al. AS01-adjuvanted vaccine alters baseline correlates of T cell response to varicella zoster virus in older adults. Vaccine, 2025 Aug 13, 61:127396.

Chan, C.C.Y., et al. AS01-adjuvanted vaccine alters baseline correlates of T cell response to varicella zoster virus in older adults. Vaccine, 2025 Aug 13, 61:127396. PMID: 40592255

• This study explores the immune mechanisms underlying the efficacy of the AS01-adjuvanted recombinant zoster vaccine (RZV) in older adults.
• It demonstrates two doses of the RZV are required to induce protective T cell responses in older adults, despite pre-existing immunity. The first dose elicits heterogeneous T cell responses and induces gene expression changes that prime the immune system, enhancing responses to the second dose. Individuals classified as fast responders (FR) exhibit higher baseline T cell counts and distinct gene expression profiles compared to slow responders (SR). Additionally, baseline gene expression and cytokine signatures associated with inflammation influence responsiveness, and the first dose can modify these gene profiles, potentially improving subsequent immune responses. 
• The study highlights that RZV alters immune cells’ gene activity, particularly related to T cell responses, which may explain the necessity of two doses for optimal vaccine efficacy in aging populations. These findings suggest potential strategies for improving vaccine efficacy in aging populations, such as modifying the baseline immune state or tailoring vaccination approaches.

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