Immunogenicity, reactogenicity and safety of three-dose primary and booster vaccination with combined diphtheria-tetanus-whole-cell pertussis-hepatitis B-reduced antigen content Haemophilus influenzae type b vaccine in Filipino children

Objectives: To evaluate the immunogenicity, reactogenicity and safety of primary and booster vaccination with DTPw-HBVLT/Hib(2.5) vaccine containing low thiomersal and reduced quantities of Hib polysaccharide (PRP). Background: Combined DTP vaccines have high global coverage. Thus, the addition of new antigens to existing DTP vaccines is the most effective way to ensure high coverage. Results: One month post-primary vaccination, 100% and >= 93.7% of subjects in both groups had anti-PRP antibody concentrations >= 0.15 mu g/mL and >= 1.0 mu g/mL, respectively. Robust responses to PRP were observed after the 10 month plain PRP challenge and booster responses were observed in unchallenged subjects after the booster dose at 15-18 months of age. Post-primary and post-booster responses to the other vaccine antigens were at least as high in the DTPw-HBVLT/Hib(2.5) group versus the DTPw-HBV/Hib(10) group. The reactogenicity profile of the DTPw-HBVLT/Hib(2.5) vaccine was acceptable. Methods: A total of 192 healthy infants were randomized to receive the investigational DTPw-HBVLT/Hib(2.5) vaccine or licensed DTPw-HBV/Hib(10) at 6, 10, 14 weeks. Immune memory to the Hib antigen was assessed through administration of plain PRP challenge at 10 months in 50% of subjects. Challenged and unchallenged subjects respectively received a DTP-HBV or DTPa-HBV/Hib booster at 15-18 months of age. Antibody responses were measured using enzyme-linked immunosorbent assay (ELISA) and reactogenicity was assessed using diary cards. Conclusion: The DTPw-HBVLT/Hib(2.5) combination vaccine with reduced thiomersal and Hib content had equivalent immunogenicity and tolerability versus the full standard DTPw-HBV/Hib(10) vaccine. DTPw-HBVLT/Hib(2.5) or DTPw-HBV/Hib(10) vaccines can contribute to reducing childhood diseases through ensuring high vaccine coverage in mass vaccination programs. ClinicalTrials.gov identifiers: NCT 01061541, NCT00158808.