Pediacel™ is currently licensed in the UK for use as a 3 dose regimen for the active immunisation of infants against Diphtheria, Tetanus, Pertussis, Poliomyelitis and invasive infections caused by Haemophilus influenzae type b. However there are currently no clinical data supporting the use of Pediacel™ using a 3, 5, and 12 months of age vaccination schedule. This study is designed to provide safety and immunogenicity data to support the use of Pediacel™ according to a 3, 5, and 12 months schedule.