[Influenza vaccination of elderly persons: state of the art].

Influenza is a major health problem among elderly people in industrialized countries. Elderly individuals suffering from chronic illnesses are more prone to suffer complications from influenza infection. In institutions, the outbreaks of influenza may touch about 60% of residents and induce life-threatening complications in more than 25% of cases. In this population--generally very old and handicapped by several chronic physical and mental diseases--the mortality associated with infections is very high. Influenza vaccination has been shown to be effective in 33% of vaccinated elderly persons for preventing clinical infection and in 74% for preventing mortality. This efficacy seems to be age-related. The other factors implicated in the immune response are discussed. A better understanding of these relationships is of great importance for public health and could improve the immune responses after influenza vaccination.