Immunogenicity and safety of Haemophilus influenzae type b polysaccharide Neisseria meningitidis conjugate vaccine in 7.5 mu g liquid formulation: A comparison of three lots with the 15.0 mu g lyophilized formulation

We conducted a multicenter, single-blind, randomized comparison of the immunogenicity and safety of three manufacturing-scale lots of 7.5 mu g liquid Haemophilus influenzae type b polysaccharide-Neisseria meningitidis conjugate vaccine (PRP-OMPC) and a single lot of 15.0 mu g lyophilized PRP-OMPC. A total of 908 infants were entered into the study. Each infant received two primary injections intramuscularly 2 months apart beginning at age 2-6 months and a booster injection at 12-15 months. Blood samples for serology were obtained before each injection and 1 month after the second and the booster dose. Immune responses were measured by radioimmunoassay. Approximately 80% of the infants achieved a titer > 1.0 mu g ml(-1) after the second primary dose of all four lots tested; the geometric mean titer (GMT) was ca 3 mu g ml(-1) for each vaccine group. After the booster dose, more than 90% of infants from each vaccine group had a titer > 1.0 mu g ml(-1); GMTs ranged from 8 to 10 mu g ml(-1). No serious vaccine-associated adverse reactions were reported. Thus the 7.5 mu g liquid PRP-OMPC vaccine was at least as immunogenic and well tolerated as the 15.0 mu g lyophilized vaccine. (C) 1997 Elsevier Science Ltd.