Inclusion Criteria:

• Toddlers previously included in Study A3L11 who completed the three-dose primary series vaccination of either DTacP-IPV-HepB-PRP-T or Infanrix hexa™ at 2, 4 and 6 months of age
• Toddlers of 15 to 18 months (456 to 578 days) of age, inclusive
• Informed Consent Form signed by at least one parent or legal representative and two mandatory witnesses
• Able to attend all scheduled visits and to comply with all trial procedures.

Exclusion Criteria:

• Participation in another clinical trial in the 4 weeks preceding the booster vaccination.
• Planned participation in another clinical trial during the present trial period.
• Congenital or acquired immunodeficiency, immunosuppressive therapy such as long-term systemic corticosteroid therapy.
• Systemic hypersensitivity to any of the vaccine components or history of a life threatening reaction to a vaccine containing the same substances.
• Chronic illness at a stage that could interfere with trial conduct or completion.
• Blood or blood-derived products received in the last 3 months.
• Any vaccination in the 4 weeks preceding the booster vaccination.
• Any vaccination planned until the next visit.
• History of documented pertussis, tetanus, diphtheria, polio, Haemophilus influenzae type b or hepatitis B infection(s) (confirmed either clinically, serologically or microbiologically).
• Administration of a vaccine against pertussis, tetanus, diphtheria, polio, Hib, and/or hepatitis B infection(s) since the end of participation in Study A3L11.
• Coagulopathy, thrombocytopenia or a bleeding disorder contraindicating intramuscular vaccination.
• Known maternal history of HIV, HB (HbsAg) or Hepatitis C seropositivity.
• Subjects with any related SAE that occurred following the three-dose primary series administration of the investigational vaccine or of the reference vaccine in Study A3L11.
• History of seizures.
• Febrile (temperature >=38.0°C) or acute illness on the day of inclusion
• Known contraindication to further vaccination with a pertussis vaccine, i.e.: Encephalopathy; Temperature >40.0°C within 48 hours following a vaccine injection, not due to another identifiable cause during the primary series; Inconsolable crying that occurred for >3 hours within 48 hours following vaccine injection during the primary series; Hypotonic hyporesponsive episode within 48 hours following vaccine injection during the primary series; Seizures with or without fever within 3 days following vaccine injection.