Multicentre Booster & Immune Memory Study of a Booster Dose of GSK Biologicals' 10-valent Pneumococcal Conjugate Vaccine or a Single Dose of 23-valent Plain Polysaccharide Vaccine in Healthy Children Aged 11-18 Mths, Previously Vaccinated in Study 103488

Inclusion criteria: Male or female between, and including, 11-18 months of age at the time of vaccination and who previously participated in the study 11PN-PD-DIT-002 and received at least one dose of pneumococcal conjugate vaccine during the primary study, free of obvious health problems 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 first dose of study vaccine, or planned use during the study period. Planned administration/ administration of a vaccine not foreseen by the study protocol during the period starting one month before the first dose of vaccine(s) and during the entire study period. Administration of any additional pneumococcal vaccine or DTPa combined vaccine since study end of 11PN-PD-DIT-002 study