Subjects previously primed with Tritanrix™-HepB/Hib-MenAC will receive Tritanrix™-HepB/Hib-MenAC or Tritanrix™-HepB/Hiberix™ vaccine (at 15-18/24 m), respectively, without or with Mencevax™ ACWY vaccine at 24 to 30 months of age. Subjects previously primed with Tritanrix™-HepB/Hiberix™ will receive Tritanrix™-HepB/Hib-MenAC or Tritanrix™-HepB/Hiberix™ vaccine (at 15-18/24 m) with Mencevax™ ACWY vaccine at 24 to 30 months of age.