The purpose of the study is to provide data on the safety and immunogenicity of Pediacel® to allow its use as a fourth dose administered to 11-18 months old toddlers at the same time as Prevenar®.

Primary Objective:

To evaluate the safety of Pediacel® booster dose co-administered with Prevenar® to toddlers at 11-18 months of age.

Secondary Objectives:

• To describe the incidence rate of severe fever within four days post-vaccination
• To describe the antibody responses to all antigens in a subgroup of subjects at baseline and post-vaccination.

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.