title: Interchangeability of 2 diphtheria-tetanus-acellular pertussis vaccines in infancy.
abstract: OBJECTIVE
  Currently, 4 diphtheria-tetanus-acellular pertussis (DTaP) vaccines are licensed for pediatric use in the United States, and 2 are commercially available. Although a single manufacturer's DTaP vaccine should be used for all 3 doses of the primary immunization series, some circumstances result in infants receiving DTaP vaccines from more than 1 manufacturer. The purpose of this study was to evaluate the safety and immunogenicity of a mixed sequence of 2 different DTaP vaccines.
  
  
  METHODS
  In this multicenter, observer-blinded, controlled study, 449 infants were randomized into 1 of 3 groups (1:1:1 ratio) to receive Tripedia at 2, 4, and 6 months of age (control group); Tripedia at 2 and 4 months of age and Infanrix at 6 months of age; or Tripedia at 2 months and Infanrix at 4 and 6 months of age. Other vaccines were administered concurrently as separate injections according to the recommended childhood immunization schedule. Safety was monitored closely, and standard enzyme immunoassays were used to measure antibody concentrations to each antigen of the DTaP vaccines.
  
  
  RESULTS
  The rates of injection-site and systemic adverse events were similar in each study group, and there were no clinically significant differences among groups after any dose. Infants in all 3 groups responded well to each antigen contained in both vaccines, with 97% to 100% seroprotection or vaccine response rates after the 3-dose primary series. Postvaccination geometric mean antibody concentrations and seroprotection or vaccine response rates to nearly all vaccine antigens were as high or higher in the mixed-sequence groups as in the control group.
  
  
  CONCLUSIONS
  Initiating the primary immunization series with 1 or 2 doses of Tripedia and completing the 3-dose series with Infanrix is as safe and at least as immunogenic as administering Tripedia for all 3 doses.
authors.affiliation: University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania 15213-2583, USA. greenbd@chplink.chp.edu
authors.forename: David P
authors.initials: DP
authors.lastname: Greenberg
authors.forename: Larry K
authors.initials: LK
authors.lastname: Pickering
authors.forename: Shelly D
authors.initials: SD
authors.lastname: Senders
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Bissey
authors.forename: Robert A
authors.initials: RA
authors.lastname: Howard
authors.forename: Mark M
authors.initials: MM
authors.lastname: Blatter
authors.forename: Keith
authors.initials: K
authors.lastname: Reisinger
authors.forename: Michael E
authors.initials: ME
authors.lastname: Pichichero
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Howe
mesh_terms: D000906:Antibodies / Q000032:analysis; D001425:Bacterial Outer Membrane Proteins / Q000276:immunology; D022681:Diphtheria-Tetanus-acellular Pertussis Vaccines / Q000008:administration & dosage / Q000009:adverse effects* / Q000276:immunology*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D016037:Single-Blind Method; D010566:Virulence Factors, Bordetella
chemical_list: D000906:Antibodies; D001425:Bacterial Outer Membrane Proteins; D022681:Diphtheria-Tetanus-acellular Pertussis Vaccines; D010566:Virulence Factors, Bordetella; C068929:pertactin