ObjectiveTo confirm that children given a bivalentHaemophilus influenzaetype b-hepatitis B vaccine (bivalent Hib-HB vaccine; COMVAX™) concurrently with priming doses of diphtheria-tetanus-pertussis vaccine (DTP), a booster dose of diphtheria-tetanus-acellular pertussis vaccine (DTaP), inactivated or oral polio vaccine (IPV or OPV) and measles-mumps-rubella vaccine (M-M-R®II) have satisfactory antibody responses to all antigens.Design126 healthy 2-month-old infants were scheduled to receive bivalent Hib-HB vaccine concurrently with DTP (2 and 4 months of age), OPV or IPV (random allocation to OPV or IPV at 2 months of age; OPV at 4 and 14 to 15 months of age), DTaP and M-M-R®II(14 to 15 months of age). A response was judged ‘adequate’ if the lower bound of the 95% confidence interval on the proportion of vaccinees having a critical antibody level was <10 percentage points below prediction.ResultsAntibodies to hepatitis B virus surface antigen,H. influenzaepolysaccharide, diphtheria toxin, tetanus toxin, pertussis agglutinogens, pertussis toxin (as measured by enzyme immunoassay but not by Chinese hamster ovary cell assay), pertussis filamentous haemagglutinin after a booster dose of DTaP, poliovirus type 2, measles virus, and mumps virus all equalled or exceeded expected levels. Antibodies to rubella virus and pertussis filamentous haemagglutinin (after priming doses of DTP) fell slightly, and in the case of rubella significantly, below predicted levels. Antibodies to poliovirus types 1 and 3 were also below expectation after 2 doses of polio vaccine but were adequate following a third dose of vaccine.ConclusionConcurrent administration of bivalent Hib-HB vaccine with priming doses of DTP, a booster dose of DTaP, OPV, IPV, or M-M-R®IIwas well tolerated and, with the possible exception of rubella, did not substantially impair the antibody response to any antigen.