Immune Responses Of Elderly Persons 4 Years After Receiving A Live Attenuated Varicella Vaccine

Annually, for 4 years after a live attenuated varicella-zoster virus (VZV) vaccine was administered to 202 elderly (55 to >87 years old) VZV-immune persons, the immune response of vaccinees was evaluated. Anti-VZV antibody levels were enhanced by vaccination for just 1 year. However, VZV-specific proliferating T cells in peripheral blood were increased in frequency from 1 in 68,000 to 1 in 40,000 at 1 year; VZV-responding T cells were still 1 in 51,000 4 years after vaccination. The calculated half-life of this enhanced immunity was 54 months. Age had little effect on response to the vaccine, but larger doses were associated with longer duration of enhanced immunity. Immunity in ∼10%-15% of vaccinees, independent of dose, failed to increase with the vaccine. This might complicate the use of this vaccine for prevention or attenuation of herpes zoster in the elderly.