1 Department of Pediatrics and the Center for Vaccine Development, University of Maryland School of Medicine, Baltimore
2 Division of Microbiology and Infectious Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, MD
3 Departments of Preventive Medicine, Medicine, Vanderbilt University School of Medicine, Nashville, TN
4 Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN
5 Department of Pediatrics, University of Rochester School of Medicine, Rochester, NY
6 Departments of Microbiology and Immunology and Pediatrics, Baylor College of Medicine, Houston, TX
7 Department of Medicine, St Louis University, Baltimore, MD
8 Departments of International Health and Pediatrics, Johns Hopkins School of Medicine and School of Public Health, Baltimore, MD
9 Departments of Microbiology and Pediatrics, Temple University School of Medicine and St Christopher's Hospital for Children, Philadelphia, PA
10 Food and Drug Administration, Rockville, MD
Objective. To evaluate the effect of simultaneous Haemophilus influenzae type b conjugate (Hib) vaccination on the safety and immunogenicity of selected acellular (DTaP) and whole-cell (DTP) pertussis vaccines with diphtheria and tetanus toxoids combined.
Methods. Enrollment of infants into a large multicenter study of the safety and immunogenicity of 13 DTaP and 2 DTP vaccines was partially completed when the first Hib vaccine, HbOC (Haemophilus b oligosaccharide conjugate vaccine), was licensed for use in infants. Thereafter, at each immunization most infants received HbOC simultaneously with DTaP (or DTP), administered in opposite thighs. Postvaccination geometric mean titers or concentrations (GMTs) of pertussis antibodies as measured by six different assays were compared pairwise among groups of infants receiving 0, 1, 2, or 3 simultaneous HbOC immunizations. The incidence of reactions was compared between infants who received only DTaP or DTP and those who received HbOC simultaneously.
Results. Comparison of postvaccination GMTs was possible among groups of infants receiving different numbers of simultaneous immunizations for 10 of the 13 DTaP and both DTP vaccines. Increased HbOC exposure had no consistent dose-response effect on antibody titers for DTaP or DTP vaccines in any assay. Significant diferences between groups in postvaccination GMTs were observed with 4 DTaP vaccines in 1 to 2 assays each; the GMTs were higher with increasing HbOC exposure for 2 DTaP vaccines and lower for 2 others. There was no significant increase in reactions with simultaneous HbOC and DTaP immunization.
Conclusions. Based on these retrospective analyses, there did not seem to be an interference in pertussis immunogenicity or alteration in reactogenicity associated with the simultaneous administration of HbOC and DTaP. These findings are encouraging with respect to the development of DTaP-Hib combination vaccines.