COMPARISON OF THE SAFETY AND IMMUNOGENICITY OF ACELLULAR (BIKEN) AND WHOLE-CELL PERTUSSIS VACCINES IN 15-MONTH-OLD TO 20-MONTH-OLD CHILDREN

Objective.-To compare the immunogenicity and reactogenicity of a two-component acellular pertussis vaccine (BIKEN) with whole-cell diphtheria and tetanus toxoids and pertussis vaccine (WC-DTP) when administered to children aged 15 to 20 months. Design.-A randomized, double-blind study. Setting.-Children in this study were from 12 general pediatric practices (11 were private and one was university-affiliated) and one inner-city university pediatric clinic. Participants.-Two hundred forty-six children aged 15 to 20 months who had received a three-dose primary series of standard WC-DTP vaccine during infancy. Selection Procedures.-Children were randomly assigned to receive either WC-DTP or one of three lots of acellular diphtheria and tetanus toxoids and pertussis vaccine (DT-aP) in a 1:3 ratio at the 11 private practices and in a 1:1 ratio at the university-affiliated practice and inner-city university pediatric clinic. Interventions.-The DT-aP vaccines contained 23.4 mug each of pertussis toxin and filamentous hemagglutinin per 0.5 mL and the same concentrations of diphtheria and tetanus toxoids as WC-DTP. Serum samples were obtained on the day of immunization and 4 to 6 weeks later. Adverse reactions at 6, 24, 48, and 72 hours were recorded by parents who were contacted by telephone at 24 and 72 hours and 14 days after immunization. Measurements/Main Results.-An indirect enzyme-linked immunosorbent assay method was used to determine IgG antibody response to pertussis toxin and filamentous hemagglutinin and IgG, IgA, and IgM to tetanus toxoids; a Chinese hamster ovary cell assay was used to measure functional antibodies to pertussis toxin; serum neutralization on VERO cells assayed diphtheria antitoxin. Recipients of the DT-aP vaccine had fewer local reactions in the first 6 to 48 hours and fewer systemic reactions at 24 hours than did recipients of the WC-DTP vaccine. Acetaminophen was administered to 31% of DT-aP recipients compared with 63% of WC-DTP recipients. Infants given DT-aP had higher geometric mean antibody titer levels against pertussis antigens after vaccination. Conclusions.-The BIKEN DT-aP vaccine used in this study is less reactogenic and more immunogenic for selected pertussis antigens than the WC-DTP vaccine in children aged 15 to 20 months.