This study evaluated the safety and immunogenicity of 3 formulations of Hib-MenCY-TT vaccine compared to 2 control groups receiving licensed meningococcal serogroup C conjugate vaccine and/or licensed Hib conjugate vaccine administered at 2, 4, and 6 months of age. Antibody persistence and immune responses to polysaccharide vaccine boosters were additionally assessed at 11 to 14 months of age.