The gracefully aging immune system.

Prolonged life expectancy in the 20th century has been one of humankind's greatest triumphs. However, the substantial increase in the human life span has ushered in a new concern: healthy aging. Because infectious diseases prominently contribute to morbidity in the particularly vulnerable elderly population, strategies for preventing these diseases would have a clear impact on improving healthy aging. Thus, vaccines and immunization strategies tailored for the elderly population are needed, and vaccines should be developed to take into consideration the peculiar age-induced variations of immune responsiveness. The conference "Ageing and Immunity" recently held in Siena, Italy, has reviewed and discussed several possible causes of immune senescence, as well as strategies for counteracting this waning of immune responsiveness and for restoring immunocompetence. In addition, examples of diseases that should be targeted by vaccination in the senior population were considered.