Both varicella and herpes zoster (HZ) can cause severe disease in certain age groups. The cell-mediated immune (CMI) response to the varicella zoster virus (VZV) is critical in preventing a recurrence of VZV. The varicella vaccine has markedly decreased the morbidity and mortality associated with varicella, but concerns linger about the cost and frequency of vaccine administration and the long-term effects on both adult varicella and HZ epidemiology in the individual and in the population. Therapy for HZ with an antiviral is only partially effective. A zoster vaccine is now available that boosts the CMI immune reaction to VZV in individuals and has proven safe and partially effective in preventing both HZ and post-herpetic neuralgia. Concerns about the zoster vaccine include the costs of administration, the overall health-care costs to society, and the acceptance and implementation of the vaccine in the elderly. Because of altered immune responses to VZV as a result of universal varicella vaccination it becomes even more compelling in the future to have a zoster vaccine ready to boost the CMI response to a sufficient level to prevent HZ. The 2 vaccines are intertwined in the future epidemiology of VZV disease.