Age-related changes in the immune response to influenza vaccination in a racially diverse, healthy elderly population.

Proliferation to phytohemagglutinin (PHA) and cell-mediated responses to influenza vaccine (FLU) were assessed in healthy elderly Caucasians, African Americans, Latinos and young Caucasians before and after immunization. Both PHA- and FLU-induced proliferation were reduced in elderly subgroups. FLU-induced proliferation increased post-vaccination in all elderly, except African Americans, but responses were lower than young. IL-2 and IFN-gamma levels did not change after vaccination of elderly, regardless of race. The altered response to FLU in elderly African Americans, compared to elderly Caucasians and Latinos, indicates that racial background is important when drawing conclusions about immune responses to FLU in mixed elderly populations.