This study was undertaken to evaluate the immunogenicity and reactogenicity of Td booster immunization in early preadolescents of Korea.

Healthy preadolescents, who had been vaccinated with 4 or 5 doses of DTaP vaccines until 6 years old age, were enrolled in this study from August 2006 to April 2007. Diphtheria and tetanus anti-toxoid antibodies in sera were measured by ELISA just before vaccination and 4 weeks after vaccination to evaluate immunogenicity. Local and systemic adverse reactions observed for 4 weeks after vaccination to access reactogenicity.

183 preadolescents were enrolled and mean age was 11.40±0.51 years old. All subjects achieved seroprotective diphtheria and tetanus anti-toxoid antibodies (titers ≥0.1 IU/mL) after Td booster vaccination. Among 183 vaccinees, 73.8% showed local adverse reactions and 37.2% systemic adverse reactions. Pain at injection site (66.1%) was the most common local reaction, and the most commonly shown systemic reaction was myalgia (17.5%). The adverse reactions were spontaneously relieved within three days after vaccination.

Td vaccine in this study was high immunogenic and showed an acceptable tolerance in Korean preadolescents. Td booster vaccination at 11-12 years old is the most effective method to increase compliance of the vaccination and to decrease the incidence of diphtheria and tetanus.