Study to Compare Booster Vaccination With Pediacel® to Infanrix® Hexa When Both Are Co-Administered With Prevenar®

Inclusion Criteria: * Toddlers 11-18 months of age (from the 11th month birthday to one day prior to the 19th month birthday) who previously received the primary immunisation series with a hexavalent vaccine (consisting of three doses of diphtheria, tetanus, pertussis, poliomyelitis, hepatitis B and Haemophilus influenza type b combined vaccine administered within the first 6 months of life) * Informed consent form signed by both parents or by the legal guardian * Parents or a legal guardian able to read and write the local language * Parents or a legal guardian able to attend all scheduled visits and to comply with the study procedures. Exclusion Criteria: * Presence of fever (defined as rectal body temperature ≥ 38.0°C) reported within the last 72 hours * Moderate or severe acute illness with or without fever * Participation in another clinical trial in the 30 days preceding study vaccination * Planned participation in another clinical trial during the present study period * Immunisation with a pneumococcal vaccine prior to study vaccination or planned during the participation in the study * Received more than 3 doses of a hexavalent vaccine prior to study vaccination * Received any vaccination in the 30 days preceding the trial * History of serological/microbiologically-confirmed diagnosis of infection due to pertussis, tetanus, diphtheria, poliomyelitis, hepatitis B, Haemophilus influenzae type b and/or Streptococcus pneumoniae * Congenital or acquired humoral/cellular immunodeficiency or immunosuppressive therapy such as long-term systemic corticosteroids therapy (≥ 2 mg/kg/day prednisone equivalent for ≥ 14 days in the 30 days prior to study vaccination) * Systemic or local hypersensitivity to any of the study vaccine components (including neomycin, streptomycin, polymyxin B and formaldehyde) * History of a life-threatening reaction (such as encephalopathy, Hypotonic-Hyporesponsive Episode (HHE), rectal body temperature ≥ 40.0°C, convulsions with or without fever) to any vaccine containing the same components as the study vaccines * Blood or blood-derived products (immunoglobulins) received during 3 months prior to study vaccination * Known HIV seropositivity * Known thrombocytopenia or a bleeding disorder contraindicating intramuscular vaccination * History of encephalopathy, seizures or progressive, evolving or unstable neurological condition * Clinically significant findings on review of systems that might interfere with study vaccination or which, in the opinion of the Investigator, would interfere with the evaluation of the study vaccine/objectives or pose a health risk to the subject.