IMMUNE-RESPONSE TO INFLUENZA VACCINATION IN A LARGE HEALTHY ELDERLY POPULATION

Elderly individuals not only demonstrate a greater risk of morbidity a nd mortality from influenza than the young, but also have greater diff iculty mounting a protective response to influenza vaccine. The mechan ism of the decreased efficacy of influenza vaccination in the elderly is not well understood. The present study was designed to assess the i nteraction between cell-mediated and humoral immune responses to influ enza vaccine in a large population (n = 233) of healthy elderly indivi duals (mean age = 80.7) living in six continuing care retirement commu nities (CCRCs). While influenza vaccination resulted in significant in creases in the mean anti-influenza antibody titres and mean proliferat ive responses of peripheral blood mononuclear cells to purified subvir ion trivalent influenza vaccine one month after vaccination, only 48.9 % and 30.0% of subjects had intact humoral and cell-mediated immune re sponses, respectively. No association was observed between intact cell -mediated and humoral responses; 14.7% of subjects had an intact cell- mediated, but not humoral response, and 32.6% of subjects had an intac t humoral, but not cell-mediated response. However, IFN gamma producti on was significantly correlated with both antibody and cell-mediated r esponses to influenza vaccination, a finding not previously reported i n the elderly. These results indicate that there is considerable heter ogeneity among immune responses of the elderly to influenza vaccinatio n. This heterogeneity needs to be a major consideration in evaluation of new vaccine preparations. (C) 1998 Elsevier Science Ltd. All rights reserved.