Background: Combined vaccines containing diphtheria-tetanus-pertussis whole-cell (DTPw), Haemophilus influenzae type b (Hib), and hepatitis-B vaccines are essential for the continuing success of vaccination programs in developing nations. This randomized, dose-ranging study assessed the immunogenicity and reactogenicity of primary and booster vaccination with pentavalent DTPw-HBV/Hib vaccines containing 10, 5 or 2.5 microg of polyribosylribitol phosphate (PRP) conjugated to tetanus toxoid (trials Hib-052/064).
Methods: Six hundred eighty infants were randomized to receive one of 5 vaccine combinations at 6, 10, and 14 weeks of age. Of these, 351 received the same vaccine at 15-24 months of age. The immune response was evaluated on blood samples collected 1 month after the 3-dose primary course and before and 6 weeks after the booster dose. Reactogenicity was assessed during a 4-day period after each vaccine dose using diary cards.
Results: After primary vaccination, all subjects had seroprotective anti-PRP antibody concentrations (> or = 0.15 microg/mL) and > 95% had concentrations > or = 1.0 microg/mL, irrespective of the PRP dose administered. Anti-PRP antibody avidity after primary vaccination and antibody persistence until the second year of life were similar among groups. The booster dose induced marked increases in anti-PRP antibody GMCs and antibody avidity, indicative of effective priming and the presence of immune memory. All vaccination regimens elicited good immune responses and comparable antibody persistence to the other vaccine antigens, with significant increases in all antibody concentrations observed after boosting. All vaccination regimens were safe, with similar overall reactogenicity profiles.
Conclusion: Hib conjugate vaccines containing reduced amounts of PRP can be effectively combined with the licensed DTPw-HBV vaccine to provide protection against 5 major childhood pathogens in a single injection.