DTPw-HB and Hib primary and booster vaccination: combined versus separate administration to Latin American children.

This multicentre study was designed to establish the reactogenicity and immunogenicity profiles of primary and booster vaccination with diphtheria, tetanus, and pertussis whole-cell-hepatitis B/Haemophilus influenzae type-b (DTPw-HB/Hib) administered as either a syringe mix or as separate injections in 400 Latin American children. Both vaccine regimens were equally well tolerated and elicited post-primary excellent seropositivity rates at or close to 100% for all five component antigens. With regard to HB, 100% of subjects in the combined vaccination group, and 98.8% subjects in the separate injection vaccination group reached seroprotective antibody concentrations (>or=10 mIU/ml) 1 month after the primary vaccination course. Equally high anti-PRP antibody concentrations were reached 1 month after vaccination, with 100% of seroprotected subjects in the combined vaccination group (antibody concentrations >or=0.15 microg/ml), against 99.4% in the separate injection vaccination group. Seroprotective anti-HBs and anti-PRP antibody concentration levels persisted approximately 1 year after the primary vaccination course, just prior to booster vaccination. Finally, a significant increase of all antibody concentrations could be observed after the booster vaccination, since all but one subject in the separate injection vaccination group had protective levels of anti-HBs and anti-PRP antibodies 1 month after the booster dose. These results suggest that the combination of DTPw-HB and Hib vaccines provides an effective means for increasing vaccine coverage in childhood vaccination programmes.