Immunogenicity of Varicella Vaccine and Immunologic Predictors of Response in a Cohort of Elderly Nursing Home Residents

BACKGROUND:  Little is known about the immunogenicity of live-attenuated Oka/Merck varicella zoster virus (VZV)-containing vaccine (hereafter, "varicella vaccine") in frail nursing homes residents nor about immune phenotypes associated with a response. METHODS:  A cohort of 190 frail nursing home residents aged 80-102 years and a cohort of 50 community-dwelling seniors aged 60-75 years (a comparison group) received varicella vaccine. Interferon γ (IFN-γ) enzyme-linked immunospot assays were performed before and 6 weeks after vaccination. Cellular markers of immunosenescence were measured in the nursing home elderly. RESULTS:  The average number of IFN-γ spot-forming cells at baseline was significantly lower in the elderly nursing home residents than in the community-dwelling seniors. However, following vaccination, the VZV immune response increased in both cohorts, and no difference was noted in the fold difference of the response between the 2 cohorts. Upon further examination of the elderly nursing home residents, we found that higher frequencies of regulatory T cells and cytomegalovirus-specific CD4⁺ T cells correlated negatively with the magnitude of VZV-specific responses. CONCLUSIONS:  The Oka/Merck varicella vaccine induces VZV immunity in elderly nursing home residents that is similar to that produced in community-dwelling seniors. CLINICAL TRIALS REGISTRATION:  NCT01328548.