Herpes zoster vaccine (ZV) was administered as a second dose to 200 participants ≥70 years old who had received a dose of ZV ≥10 years previously (NCT01245751).

Varicella zoster virus (VZV) antibody titers (measured by a VZV glycoprotein–based enzyme-linked immunosorbent assay [gpELISA]) and levels of interferon γ (IFN-γ) and interleukin 2 (IL-2; markers of VZV-specific cell-mediated immunity [CMI], measured by means of ELISPOT analysis) in individuals aged ≥70 years who received a booster dose of ZV were compared to responses of 100 participants aged 50–59 years, 100 aged 60–69 years, and 200 aged ≥70 years who received their first dose of ZV. The study was powered to demonstrate noninferiority of the VZV antibody response at 6 weeks in the booster-dose group, compared with the age-matched first-dose group.

Antibody responses were similar at baseline and after vaccination across all age and treatment groups. Both baseline and postvaccination VZV-specific CMI were lower in the older age groups. Peak gpELISA titers and their fold rise from baseline generally correlated with higher baseline and postvaccination VZV-specific CMI. IFN-γ and IL-2 results for subjects ≥70 years old were significantly higher at baseline and after vaccination in the booster-dose group, compared with the first-dose group, indicating that a residual effect of ZV on VZV-specific CMI persisted for ≥10 years and was enhanced by the booster dose.

These findings support further investigation of ZV administration in early versus later age and of booster doses for elderly individuals at an appropriate interval after initial immunization against HZ.

NCT01245751.