Vaccination With GSK 1024850A in Children Primed With GSK 1024850A & Boosted With Pneumovax 23™

The aim of this study is to assess the immune response, safety and reactogenicity following administration of an additional dose of a pneumococcal conjugate vaccine at approximately 4 years of age in children previously vaccinated with 3 primary doses of GSK 1024850A or Prevenar™ vaccine within the first 6 months of life and a booster dose of plain polysaccharide pneumococcal (Pneumovax 23™) vaccine at 11-14 months of age. Antibody persistence will also be assessed at approximately 4 years of age in children previously vaccinated with 3 doses of either GSK 1024850A or Prevenar™ vaccine followed by a booster dose of Pneumovax 23™. This protocol posting deals with objectives \& outcome measures of the extension phase at year 4. The objectives \& outcome measures of the primary phase are presented in a separate protocol posting (NCT 00307541). The objectives \& outcome measures of the booster phase are presented in a separate protocol posting (NCT 00333450).