Goals for immunization in older adults may differ from those in young adults and children, in whom complete prevention of disease is the objective. Often, reduced hospitalization and death but also averting exacerbation of underlying chronic illness, functional decline, and frailty are important goals in the older age group. Because of the effect of age on dendritic cell function, T cell-mediated immune suppression, reduced proliferative capacity of T cells, and other immune responses, the efficacy of vaccines often wanes with advanced age. This article summarizes the discussion and proceedings of a workshop organized by the Association of Specialty Professors, the Infectious Diseases Society of America, the American Geriatrics Society, the National Institute on Aging, and the National Institute of Allergy and Infectious Diseases. Leading researchers and clinicians in the fields of immunology, epidemiology, infectious diseases, geriatrics, and gerontology reviewed the current status of vaccines in older adults, identified knowledge gaps, and suggest priority areas for future research. The goal of the workshop was to identify what is known about immunizations (efficacy, effect, and current schedule) in older adults and to recommend priorities for future research. Investigation in the areas identified has the potential to enhance understanding of the immune process in aging individuals, inform vaccine development, and lead to more-effective strategies to reduce the risk of vaccine-preventable illness in older adults.