Immunoassay of diphtheria and tetanus according to ages

Background: The objective of this study was to evaluate protective immunity against diphtheria and tetanus in the Korean population. Materials and Methods: Healthy subjects were enrolled at four university hospitals in Korea. Subjects were assigned to seven age groups (every 10 years). Enzyme linked immunosorbent assay (ELISA) kits were used for measurement of diphtheria or tetanus anti-toxoid antibodies in sera, and geometric mean concentrations (GMC) of antibodies were determined. Subjects with antibody titers <0.1 IU/mL would require a booster vaccination. Results: A total of 1,605 subjects participated in this study. In analysis of antibody against diphtheria, subjects in the age group <11 yr showed the highest GMC (1.31 IU/mL) while the lowest GMC was observed in subjects in the 31-40 yr age group (0.17 IU/mL). With regard to tetanus, subjects in the age group <11 yr also showed the highest GMC (1.81 IU/mL). Among subjects ≥11 yr (600 subjects), 363 (60.5%) would require a diphtheria booster, and 422 (70.4%) would require a tetanus booster. Conclusions: GMC of antibodies against diphtheria and tetanus of adolescents and adults were relatively low, while those of children in Korea were satisfactory. Approximately two-thirds of Korean adolescent and adult subjects in this study would require a booster vaccination in order to maintain long-term protective immunity against diphtheria and tetanus.