This is a single-blind, open-label, randomised controlled trial with five groups. There are four different Pneumococcal Conjugate Vaccine (PCV) schedules to be evaluated.

This is a single-blind, open-label, randomised controlled trial with five groups. There are four different PCV schedules to be evaluated: a 0+1 schedule of PCV10 at 12 months of age (Group V), a 0+1 schedule of PCV13 at 12 months of age (Group W), a 1+1 schedule of PCV10 at 2 and 12 months of age (Group X), and a 1+1 schedule of PCV13 at 2 and 12 months of age (Group Y); along with a control group that receives a dose of PCV10 at 24 months of age (Group Z). Additionally, all participants will receive four doses of Infanrix-hexa at 2, 3, 4 and 18 months of age.

Inclusion Criteria:

• Aged between 2 months and 2 months plus 2 weeks;
• No significant maternal or perinatal history;
• Born at or after 36 weeks gestation;
• Written and signed informed consent from parent/legal guardian;
• Lives within approximately 30 minutes of the commune health centre;
• Family anticipates living in the study area for the next 22 months

Exclusion Criteria:

• Known allergy to any component of the vaccine;
• Allergic reaction or anaphylactic reaction to any previous vaccine;
• Known immunodeficiency disorder;
• Known HIV-infected mother;
• Known thrombocytopenia or coagulation disorder;
• Administration or planned administration of any immunoglobulin or blood product since birth;
• Severe birth defect requiring ongoing medical care;
• Chronic or progressive disease;
• Seizure disorder;
• History of severe illness;
• Receipt of any 2 month vaccines through the Expanded Programme of Immunization (EPI) program;
• Family plans on giving the infant Quinvaxem (DTP-Hib-HBV).

Additionally, enrolment will be deferred and infants asked to return to the health centre one week later for reassessment if they have at least one of the following deferral criteria:

• Axillary temperature ≥37.5°C or ≤35.5°C;
• Acute infection, especially bacterial;
• Oral administration of corticoid therapy in past 14 days; or
• Any of the following symptoms that interfere with normal activities: crying more than usual, sleeping more than usual, or loss of appetite.

This is a single-blind, open-label, randomised trial, with laboratory staff blinded to study group allocation as all the outcome measures that address the study objectives are laboratory based. Laboratory samples will be labelled with a unique trial identification number that does not identify the study group. Given the different timing of the vaccine schedules in the different study arms, the study nurses, vaccine administrators and participants will not be blinded to the study group allocation of each infant.