This is a follow-on, multi-centre, open-label, clinical trial. The purpose of this trial is to investigate the concentrations of serotype-specific antibodies to IgG included in PCV13 in children who have received either the PCV7 or PCV13 primary immunisation at 2, 4 and 12 months of age. We intend to recruit all interested participants who completed the Wyeth-sponsored PCV13 infant trial study (6096A1-007) at selected study sites (i.e. those that recruited the majority of the children in the original study). The study will start in March 2010, at which time the eldest participants in the 6096A1-007 study will be approximately 42 months of age. There will be two visits per participant, 1 month apart from each other. At visit one, all participants will have a blood test and receive a dose of PCV13. At visit 2, all participants will have a blood test and will be offered the remaining pre-school booster vaccinations unless they have already received them.

Inclusion Criteria:

1. Participant completed the Wyeth-sponsored PCV13 infant trial study (6096A1-007) at one of the study sites participating in this follow-on study.
2. Aged 39-46 months (inclusive) at time of enrolment.
3. Available for entire study period and whose parent/legal guardian can be reached by telephone.
4. Healthy children as determined by medical history, physical examination, done by a study nurse (and/or study doctor if required, depending on the medical history of the participant and physical assessment), and judgment of the investigator.
5. Parent/legal guardian must be able to complete all relevant study procedures during study participation.

Exclusion Criteria:

1. Has received further doses of pneumococcal vaccination with licensed or investigational pneumococcal vaccine other than those given as part of the Wyeth-sponsored PCV13 infant trial study (6096A1-007).
2. A previous anaphylactic reaction to any vaccine or vaccine-related component.
3. Contraindication to vaccination with pneumococcal conjugate vaccine.
4. Bleeding diathesis or condition associated with prolonged bleeding time that would contraindicate intramuscular injection.
5. Known or suspected immune deficiency or suppression.
6. History of culture-proven invasive disease caused by S pneumoniae.
7. Major known congenital malformation or serious chronic disorder.
8. Significant neurologic disorder or history of seizures including febrile seizure, or significant stable or evolving disorders such as cerebral palsy, encephalopathy, hydrocephalus, or other significant disorder.
9. Receipt of blood products or gamma-globulin (including hepatitis B immunoglobulin and monoclonal antibodies; eg, synagisB).
10. Participation in another investigational study other than the Wyeth-sponsored PCV13 infant trial study (6096A1-007). Participation in purely observational studies is acceptable.
11. Child who is a direct descendant (child, grandchild) of the study site personnel.