[Immune reaction to tetanus in the elderly: what is the duration of vaccine protection?].

Infectious diseases represent one of the most frequent causes of morbidity and mortality in the elderly. Little information is yet available on the state of immunization against well-known antigens such as tetanus toxoid (TT) in old age. It was, therefore, the aim of this study to analyze antibody titres and peripheral blood mononuclear cell (PBMC) reactivity to TT in healthy SENIEUR compatible young (< 30 years, n = 25) and old (> 65 years, n = 32) blood donors. TT-specific antibodies were measured by the ELISA technique; PBMC proliferation was assessed by 3H-thymidine incorporation analysis. In the young group TT antibody titres were detectable in all but two individuals, whereas 60% of the old persons had no detectable TT antibodies. This seemed partly to be due to a shortened immunological memory in old age, since 32% of the aged persons without TT antibodies had been vaccinated within the past 10 years, 21% even 3 to 6 years prior to investigation. TT antibody concentrations were normal in aged individuals vaccinated within the past two years. Peripheral blood lymphocytes from all but two persons without antibody titres did not proliferate when stimulated with TT in vitro, indicating that no memory T cells were available to reinduce an efficient immune response. Our results suggest that the tetanus vaccination strategy practised in Austria does not guarantee full protection in the elderly.