Prevalence of diphtheria and tetanus antibodies and circulation of Corynebacterium diphtheriae in Sao Paulo, Brazil

The introduction of routine vaccination against tetanus and diphtheria in Brazil has decreased the incidence and changed the epidemiology of both diseases. We then investigated the prevalence of Corynebacterium diphtheriae carrier status and diphtheria and tetanus immunity in Sao Paulo, Brazil. From November 2001 to March 2003, 374 individuals were tested for the presence of C. diphtheriae in the naso-oropharynx and of serum diphtheria and tetanus antibodies. Participants were all healthy individuals without acute or chronic pathologies and they were stratified by age as follows: 0-12 months and 1-4, 5-9, 10-14, 15-24, 25-39, 40-59, and >= 60 years. Antibodies were assessed using a double-antigen ELISA. C. diphtheriae species were identified by biochemical analysis and toxigenicity was assessed by the Elek test. For diphtheria, full protection (antibodies >= 0.1 IU/mL) was present in 84% of the individuals, 15% had basic protection ( antibodies >= 0.01 and <0.1 IU/mL) and 1% were susceptible (antibodies <0.01 IU/mL). Full tetanus protection (antibodies >= 0.1 IU/mL) was present in 79% of the participants, 18% had basic protection ( antibodies >= 0.01 and <0.1 IU/mL) and 3% were susceptible ( antibodies <0.01 IU/mL). The geometric mean of diphtheria and tetanus antibodies reached the highest values at 5-9 years and decreased until the 40-59-year age range, increasing again in individuals over 60 years. Three participants (0.8%) were carriers of C. diphtheriae, all non-toxigenic strains. The present results demonstrate the clear need of periodic booster for tetanus and diphtheria vaccine in adolescents and adults after primary immunization in childhood.