Objective: To determine antibody levels to the Australian manufactured combined diphtheria, tetanus and pertussis (DTP) vaccine (Triple Antigen, CSL Ltd) in infants before and after their primary immunization course.
Methodology: Serosurvey (antibody prevalence study) in two groups: infants aged 5-9 weeks who had not received any immunizations (n = 25), and infants aged 7-10 months who had received two (n = 25) or three immunizations (n = 57) with DTP, sampled from infants attending the Royal Children's Hospital, Melbourne, either as inpatients or outpatients between February and April 1993. The immunization history for each infant was determined from hospital records, the parent-held child health record, or the local council or family doctor who immunized the infant.
Results: Enzyme immunoassay (EIA) of antibodies to diphtheria and tetanus showed all infants to have adequate protective levels after two or three vaccinations (> or = 0.01 IU/mL). All subjects who had received all three DTP vaccinations had detectable antibody to at least one pertussis antigen. Antibodies to the pertussis antigens filamentous haemagglutinin and pertussigen (pertussis toxin) were comparable to levels determined for whole cell pertussis vaccines used elsewhere in the world. EIA-determined antibodies to pertussis agglutinogen type 2 and agglutinogen type 3 showed substantially higher geometric mean titres when results for pre-immunization and post-immunization subjects were compared.
Conclusions: These data show that the Australian manufactured DTP vaccine has immunogenic properties similar to those of vaccines used elsewhere, and that antibody concentrations following immunization are at levels consistent with efficacy.