Safety and Immunogenicity Study of a Booster Dose of GSK Biologicals' 10-valent Pneumococcal Conjugate Vaccine.

To Assess the Safety, Reactogenicity & Immunogenicity of a 4th Dose of GSK Biologicals' Pneumococcal Vaccine or Prevenar™ in Children (12-18 Months) Previously Vaccinated in the Primary Study NCT00307554 With Either Pneumococcal Vaccine or Prevenar™

This study will evaluate the safety, reactogenicity and immunogenicity of a booster dose of GSK Biologicals' pneumococcal conjugate vaccine compared to Prevenar™ given at 12-18 mo of age to children primed with either pneumococcal vaccine or Prevenar™ in study 105553. Antibody persistence will be evaluated at 8-14 mo after completion of the 3-dose immunization course in study 105553 (NCT00307554). The immune response to a booster dose of GSK Biologicals' pneumococcal conjugate vaccine will also be evaluated when given at 12-18 mo to subjects not primed with GSK Biologicals' vaccine but with Prevenar™.

The study has 3 groups. 1 group of children primed with GSK Biologicals' pneumococcal conjugate vaccine will receive a booster dose of the same vaccine. 2nd group of children primed with Prevenar™ will receive a booster dose of Prevenar™ (control group). 3rd group of children primed with Prevenar™ will receive a booster dose of GSK Biologicals' pneumococcal conjugate vaccine. All children will receive concomitantly a booster dose of DTPa-HBV-IPV/Hib vaccine.

Inclusion Criteria:

• a healthy male or female, 12 to 18 months of age at the time of vaccination, who received at least one dose of either pneumococcal conjugate vaccine or Prevenar™ during study 105553 and with written informed consent obtained from the parent/guardian of the subject.

Exclusion Criteria:

• use of any investigational or non-registered drug or vaccine other than the study vaccine within 30 days preceding the vaccination, or planned use during the entire study period (active phase and safety follow-up).
• Planned administration/ administration of a vaccine not foreseen by the study protocol during the period starting one month before vaccination up to Visit 2.
• Administration of any additional pneumococcal vaccine or DTPa-combined vaccine since end of study 105553. Children with a history of seizures or neurological disease, allergic disease, immunosuppressive or immunodeficient condition.