A new DTPw-HBV/Hib vaccine: Immune memory after primary vaccination and booster dosing in the second year of life

The response to booster vaccination at 15-18 months of age and the presence of immune memory in 10-month old children, primed with a new combined diphtheria-tetanus-hepatitis B-whole cell pertussis vaccine extemporaneously mixed with Haemophilus influenzae type b-tetanus toxoid conjugate (DTPw-HBV/Hib) from new antigen sources and containing 2.5 microg polyribosyl-ribitol-phosphate (PRP) was assessed. Primary vaccination with the new DTPw-HBV/Hib vaccine was immunogenic and of comparable tolerability to commercially available Tritanrix HepB/Hiberix. Children were boosted with DTPw-HBV, DTPw-HBV/Hib or separate DTPw-HBV+Hiberix. Immune memory was assessed through administration of 10 microg PRP polysaccharide. Anti-PRP antibody GMCs increased substantially after the challenge in DTPw-HBV/Hib-primed subjects indicating the presence of immune memory. One month after the booster dose, 100% of subjects had seroprotective antibody concentrations against PRP, diphtheria and tetanus, >95% were seroprotected against hepatitis B, > or =94.0% had a pertussis booster response. Substantial increases in antibody GMCs against all antigens were observed. Swelling >20 mm was the most common Grade 3 solicited symptom reported (up to 26.0% of subjects). Fever >39.5 degrees C was uncommon (>2.5%). Eleven large swelling reactions were reported; none involved an adjacent joint. One serious adverse event occurred that was considered unrelated to vaccination. This new DTPw-HBV/Hib vaccine with new vaccine components and 2.5 microg PRP induced effective priming against Hib evidenced by a vigorous anamnestic response on exposure to PRP polysaccharide. The booster dose was immunogenic and the safety profile was acceptable. Combined DTPw-HBV and DTPw-HBV/Hib vaccines using new vaccine antigen sources will promote continued supply of combined DTPw-based vaccines to global mass vaccination campaigns.