IMMUNOGENICITY AND REACTOGENICITY ASSOCIATED WITH AN 18-MONTH BOOSTERDOSE OF A NEW DIPHTHERIA-TETANUS-WHOLE CELL PERTUSSIS-VACCINE

Objective: To establish safety and immunogenicity of a reformulated wh ole cell pertussis based diphtheria-tetanus-pertussis vaccine (DTP,) a t the 18-month booster stage following a 2,4, and 8-month primary immu nisation course. Method: Open trial in suburban Melbourne in 100 healt hy children initially recruited through maternal and child health cent res. Thirty-five subjects were bled prior to vaccination, and 4-6 week s after vaccination. A 7-day diary card was used to record subject tem peratures and other systemic and local clinical signs. Results: The in crease in antibody geometric mean titres (GMT) after boosting was 19.6 -fold (95% ci 14.2, 27.2) for tetanus and 26.5-fold (95%ci 16.6, 42.4) for diphtheria. Pertussis antibody GMTs also all showed substantial i ncreases following the booster, with mean fold changes in titre rangin g from 7.3 (Agg2) to 31.3 (Fha). Seventeen percent of subjects (95%ci 10%, 26%) experienced axillary temperatures greater than or equal to 3 8 degrees C during the 24-h period following vaccination. Low rates of significant (>25 mm) injection site redness (13%) and swelling (8%) w ere recorded at 24 h postvaccination. Conclusion: This vaccine was wel l tolerated by children at 18 months of age, and showed substantial bo osting of antibody to all components.