Immunologic response to a single dose of tetanus toroid in older people

OBJECTIVES: Several studies have demonstrated that a large percentage of ol der people are inadequately immunized against tetanus. The aim of this stud y was to assess the immunity against tetanus in a group of individuals aged 69 and older and to examine the immune response to a single dose of tetanu s toroid. DESIGN: A convenience sample of 115 residents of a large retirement home, a ged 69 and older, was studied. After a blood sample for anti-tetanus antibo dy titer, a single dose of tetanus toroid vaccine was administered. Repeat titers were obtained 6 weeks after the Vaccination and analyzed by ELISA as say. Antibody levels equal to or greater than 0.1IU/mL were considered prot ective. RESULTS: Sixty-seven of 115 (58.3%) individuals had adequate antibody titer s. Those individuals who reported having been vaccinated with tetanus toroi d in the past were more likely to be immunized adequately compared with tho se who reported having never been vaccinated (66.7% vs 39.3%, P = .02). Aft er vaccination, 34 of 46 (73.9%) individuals with inadequate antibody titer s became seropositive. Those who remained seronegative had mean prevaccinat ion antibody titers significantly lower than those who seroconverted. Sixte en of 17 (94.1%) persons who reported having been vaccinated in the past an d were found to be seronegative developed adequate antibody titers followin g vaccination, compared with only nine of 16 (56.2%) who reported never hav ing been vaccinated (P = .04). There was no association between seroconvers ion rate and age, sex, underlying diseases, and army service. CONCLUSIONS: Most individuals will develop an adequate anti-tetanus antibod y titer following administration of a single dose of tetanus vaccine. A his tory of past immunization is a good predictor of becoming adequately immuni zed. It is important that physicians follow the current recommendations for adult immunization and initiate campaigns to ensure that the older populat ion is protected against tetanus.