The purpose of the study is to evaluate the immunogenicity, safety and reactogenicity of a booster dose of DTPw-HBV/Hib-MenAC compared to DTPw-HBV/Hib given to healthy subjects at 15 to 24 months of age primed with 3 doses of Tritanrix™-HepB/Hib-MenAC in study 100480. Antibody persistence will be evaluated at 24 to 30 months. Immunogenicity, safety and reactogenicity of a dose of Mencevax™ ACWY given at 24 to 30 months will also be evaluated when given to subjects not boosted with a MenA conjugate and/or MenC containing vaccine.