Immunity to influenza in the elderly

influenza is caused by a constantly varying segmented RNA virus that necess itates yearly review of vaccine composition. Humans over the age of 65 year s are considered at high risk from influenza; during influenza epidemics th e rate of hospitalization in the elderly is very high and up to 90% mortali ty can occur. Vaccination of the elderly has been shown to be efficacious a nd cost effective but immunological senescence in the institutionally confi ned frail elderly is demonstrated by failure to induce herd immunity after vaccination. Reductions in B- and T-cell immunity and in levels of interleu kin-2 are age related. Attempts to increase the immunoresponsiveness of the elderly to influenza vaccines have given mixed results. The most convincin g evidence is in rodents where dietary caloric restriction has been shown t o enhance viral immunity. (C) 2000 Elsevier Science Ltd. All rights reserve d.