Recent developments in the field of immune memory research and the accumulating literature on age-related alterations in homeostasis, primary and memory T cell responses make it pertinent to address whether and how memory responses are affected by aging with regard to their generation, maintenance, and protective function. New knowledge of T cell repertoire maintenance over long periods of time, particularly when confronted with persistent pathogen challenge, is now enriched further by studies on whether recent immunological memory can 'overfill' and/or constrict prior memory responses. Along with studies on potentiation of memory responses by dietary/metabolic interventions and the recent advances on regulation of primary responses with aging, these findings provide a platform for new approaches to vaccination of older adults.