Worldwide, herpes zoster (HZ) affects millions of patients (particularly older adults) annually and causes significant suffering due to acute and chronic pain, or postherpetic neuralgia (PHN). The objective of this article is to explain the rationale for the HZ vaccine by summarizing data on the epidemiology of HZ in the immunocompetent host, with a focus on recent incidence and risk factor studies; to review information on the burden of HZ; and to discuss the challenges of lessening the morbidity of the disease. The incidence and severity of HZ and PHN are highest in older adults. Given the central nervous system damage caused by HZ, the difficulty of adequately treating HZ to prevent PHN, and the intractability of PHN, the advent of the HZ vaccine appears to be a crucial innovation for preventing HZ and PHN.