The seroprevalence of diphtheria among adults in Izmir-Turkey.

A serological survey to determine the immunity to diphtheria in the adult population in Izmir-Turkey was conducted according to the recommendations of the World Health Organization. A total of 339 blood samples were collected from subjects aged between 20 and 81, and diphtheria antitoxin levels were measured by the enzyme linked immunosorbent assay method. Titers below 0.1 IU/ml were considered to show insufficient immunity. Of the studied population, 56.3% had showed insufficient immunity against diphtheria. Diphtheria protection rates showed a gradual age-related decrease. The lowest immunity rate was observed in 40-49-year age group (30.6%) (p<0.05). There was no significant difference in the rate of immunity between subjects in terms of sex, levels of education, urban-rural region (p>0.05). These results emphasize the need for booster immunization of adults. The present vaccination policy should include re-vaccinations of the adult population every 10 years in order to provide a complete protection of the population.