Fading immune protection in old age: Vaccination in the elderly.

The function of the immune system declines with age, causing an increased occurrence and severity of infectious diseases and a decreased response to vaccines (Grubeck-Loebenstein et al., 2009). As the thymus gradually loses its ability to replenish the population of naïve T cells, the memory and effector T cells increase in number and dominate the repertoire. The changes in the naïve and memory T cell pool that occur with aging in humans are discussed here, along with a brief update of the knowledge of B cell populations in the elderly