Immunology of Varicella Immunization in the Elderly

OBJECTIVE: To review the varicella-zoster virus (VZV) and herpes zoster disease and to summarize published reports on the use of the live-attenuated varicella zoster vaccine to enhance cell-mediated immunity in elderly individuals. DATA SOURCE: A MEDLINE search (1966-August 1999) for English-language clinical studies and review articles pertaining to VZV and the live-attenuated varicella vaccine was conducted; references obtained from these publications were subsequently reviewed for additional relevant articles. STUDY SELECTION AND DATA EXTRACTION: Representative clinical trials were summarized and relevant information was selected to assist in the understanding of VZV, the subsequent immune response, and the live-attenuated varicella vaccine. DATA SYNTHESIS: The physiologic, age-related decline in VZV cell-mediated immunity has been shown to be restored on administration of live-attenuated varicella vaccine. Various studies report serum anti-VZV antibody concentrations, and production of interferon-gamma were increased following vaccination. Concentrations subsequently returned to baseline one year after vaccination. Increase in responder cell frequency, a measure of cell-mediated immunity, has been reported to last up to four years after vaccination, at concentrations similar or superior to those observed following herpes zoster. CONCLUSIONS: Enhancement of cell-mediated immune response in elderly individuals through vaccination with live-attenuated varicella vaccine is a possible measure to protect this population from herpes zoster and to attenuate its complications. A summary of immunogenicity studies to identify the immune response to live-attenuated varicella vaccine in the elderly is presented. The absolute clinical significance, as well as appropriate administration guidelines of this prophylactic intervention, will become evident following forthcoming large, masked, placebo-controlled trials.