Prevalence of hyperimmunization against tetanus in Italians born after the introduction of mandatory vaccination of children with tetanus toxoid in 1968.

Systematic mandatory immunization of children against tetanus was started in Italy in 1968. Prevalence of tetanus hyperimmunization (> 5 IU/ml) was assessed among 214 immune subjects born after 1968 and found to be 17.3%. This figure is significantly higher (p < 0.01) than the 10.8% found in a previous study of subjects born before 1968. This increase is statistically significant in the Center (p < 0.01) and in the South (p < 0.05) of Italy, but not in the North. Hyperimmunization is not associated with family size (odds ratio 2.16; C. I. 95% = 0.5-7.6) or the father's years of education (odds ratio 1.83; C. I. 95% = 0.6-5.3). No difference was found between urban and rural areas of residence. Indiscriminate administration of booster doses of tetanus vaccine in hyperimmune subjects in some areas could result in unnecessary vaccinations, which can cause hypersensitivity reactions.