Diphtheria immunity of different age groups in Turkey

In Turkey, the immunization policy against diphtheria involves childhood vaccination, and no routine booster dose is administered after 12 years of age. Information about the immune status of the population is important to predict the potential for epidemics, several of which have occurred recently in neighboring countries. The aim of this study was to assess the immune status of different age groups in Turkey against diphtheria. A total of 497 blood samples were collected, 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. Overall, 35.8% of the population studied showed insufficient immunity against diphtheria. Immunity rates varied significantly among different age groups (P < 0.01). Protective immunity rates were highest in the 3- to 6-year age group (81.3%) and the over 60 age group (81.2%). In subjects between the ages of 10 and 59 the percentage of people with insufficient immunity was above 30%. The lowest immunity rate was observed in 20- to 29-year age group. No significant difference was seen between males and females in terms of protective effect of vaccination. This study indicates that people between the ages of 10 and 59 are susceptible to diphtheria in our country. Therefore, revaccination of adults with tetanus-diphtheria toxoids at every opportunity (military service, pregnancy, admittance to emergency room) should be considered as an immunization policy.