Background: Study assessed the immunogenicity and safety of an investigational Haemophilus influenzae type b-Neisseria meningitidis serogroups C and Y–tetanus toxoid conjugate vaccine (HibMenCY-TT) in infants.
Methods: In a single-blinded, controlled study, 609 infants were randomized 1:1 to receive primary vaccination (2, 4, and 6 months) with either HibMenCY-TT or monovalent Haemophilus influenzae type b tetanus toxoid conjugate vaccine (Hib-TT), co-administered with combined diphtheria-tetanus-acellular pertussis-hepatitis B-inactivated poliovirus vaccine and 7-valent pneumococcal conjugate vaccine. A second control group of 3- to 5-year-old children received a single dose of licensed meningococcal ACWY polysaccharide vaccine (MPSV4). Immunogenicity was measured before and 1 month after dose 3/MPSV4 using human (hSBA) and rabbit complement bactericidal assays (rSBA) and enzyme-linked immunosorbent assay assays for IgG antibodies to MenC and MenY polysaccharides. Anti-polyribosylribitol phosphate antibody concentrations were measured 1 month after the third dose. Safety was also assessed.
Results: One month after primary vaccination statistically significantly more HibMenCY-TT than Hib-TT vaccines had anti-PRP antibody concentrations ≥1.0 μg/mL (93.5% vs. 85.8%). The percentage of HibMenCY-TT recipients with hSBA titers ≥1:8 (MenC: 95.9%, MenY: 89.4%) was statistically significantly higher than for MPSV4 recipients (MenC: 30.2%, MenY: 47.5%). The percentage of subjects reporting any severe (grade 3) symptom within 4 days of each vaccination was: 11.5% (HibMenCY-TT) and 24.8% (Hib-TT) (group difference, 13.27%, 95% CI: [7.22;19.29], P < 0.001).
Conclusion: The investigational HibMenCY-TT vaccine was well tolerated and immunogenic in infants, induced Hib immune responses that were comparable to licensed Hib-TT vaccine, and induced high levels of bactericidal antibodies against N. meningitidis serogroups C and Y.