Prevalence of IgG diphtheria antitoxin in blood donors in Rio de Janeiro

The lack of information on the immunity of adults in Brazil against diphtheria prompted us to analyse sera from 234 blood donors aged 18–61 years (30·3% females and 69·7% males). IgG diphtheria antitoxin levels determined by means of an ELISA, validated by toxin neutralization test in Vero cells, showed that 30·7% (95% CI 25·0–37·1) of the population was fully protected ([ges ]1 IU/ml). The highest percentage of subjects fully protected was in the 31–40 years age group. Most of the subjects with uncertain or no protection (