Immune senescence and vaccines to prevent herpes zoster in older persons.

Varicella-zoster virus (VZV) T-cell-mediated immunity (VZV-CMI) in older persons prevents latent VZV in sensory neurons from reactivating to cause herpes zoster. VZV-CMI declines greatly with aging, but can be restored by the licensed zoster vaccine. However, the vaccine-induced boost in VZV-CMI (which determines the efficacy of the vaccine) is a function of the age of the vaccinee, and the duration of this boost wanes with time. Both factors influence the value of this vaccine. To understand these aging effects, limited information about the phenotypic and functional differences in VZV-CMI in old and young persons are reviewed, as well as the reversal of these differences by vaccination. Based on information from these studies some potential approaches to improving prevention of herpes zoster are discussed.