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.

Inclusion Criteria:

• Infants aged 80 to 120 days inclusive on the day of inclusion.
• Born at full term of pregnancy (> 37 weeks)
• Informed consent form signed by the parent(s) or other legal representative according to local regulations
• Parent(s) or legal representative able to attend all scheduled visits and to understand and comply with the study procedures (able to read and write; access to a telephone).

Exclusion Criteria:

• Rectal temperature ≥ 38.0°C
• Moderate or severe acute illness with or without fever
• Participation in another clinical trial in the 4 weeks preceding the first trial vaccination
• Having received any DTaP, IPV, or Hib vaccines prior to study initiation or any vaccination in the 4 weeks preceding the first trial vaccination
• Planned participation in another clinical trial during the present trial period
• Known history of diphtheria, tetanus, pertussis, H. influenzae type b infections, poliomyelitis
• Congenital or acquired immunodeficiency, immunosuppressive therapy such as long-term systemic corticosteroids therapy
• Systemic hypersensitivity to any of the vaccine components (including neomycin, streptomycin, polymyxin B and formaldehyde)
• History of a life-threatening reaction (such as encephalopathy, Hypotonic Hyporesponsive Episode, severe fever, convulsions, etc.) to the trial vaccine or a vaccine containing the same substances
• Blood or blood-derived products (immunoglobulins) received in the past 4 weeks
• Vaccination planned in the 6 weeks following any trial vaccination
• Known HIV seropositivity
• Thrombocytopenia or a bleeding disorder contraindicating intramuscular vaccination
• History of seizures or progressive, evolving or unstable neurological condition
• Clinically significant findings on review of systems that might interfere with correct vaccination or which, in the opinion of the Investigator, would interfere with the evaluation of the vaccine or pose a health risk to the subject.