This study evaluated the safety and immunogenicity of 3 formulations of Hib-MenCY-TT vaccine and 1 formulation of Hib-MenC-TT vaccine compared to a control group receiving licensed meningococcal serogroup C conjugate vaccine, each administered at 2, 3, and 4 months of age. Antibody persistence and immune responses to booster vaccinations were additionally assessed at 12 to 18 months of age.