This study evaluates the immunogenicity and consistency of 3 Hib-MenCY-TT vaccine lots and the safety and immunogenicity of Hib-MenCY-TT vaccine compared to a control group receiving licensed Hib conjugate vaccine, when each are co-administered with Pediarix® to healthy infants at 2, 4, and 6 months of age. The study will also evaluate the safety and immunogenicity of Hib-MenCY-TT vaccine compared to a control group receiving licensed Hib conjugate vaccine, when each are co-administered with M-M-R® II and Varivax® at 12 to 15 months of age.