<qa>  What is immunosenescence?Deleterious changes in immunity that occur with aging are known as immunosenescence. Such changes, particularly in adaptive immunity, may lead to an impaired vaccine response in the elderly. Characterizing the immune determinants and the genetic basis for vaccine response in the frail elderly is a practical approach to better our understanding of immunosenescence. Data on genetic determinants to immunization are sparse, furthermore, to the best of our knowledge, none exist in the elderly. In this pilot study, we propose studying the immune response to the herpes zoster vaccine and the underlying genetic determinants of the immune response in elderly residents of nursing homes. 