Inclusion Criteria:

• Healthy infants, 19 weeks of age, with weight for age z-scores within 2 standard deviations of normal.
• Have received all standard EPI immunizations according to national immunization programme.
• Written informed consent by parent.
• Mother HIV-1/2-uninfected.

Exclusion Criteria:

• Acute disease at the time of vaccination (acute disease is defined as the presence of a moderate or severe illness with or without fever). All vaccines can be administered to persons with a minor illness such as diarrhoea, mild upper respiratory tract infection with or without low-grade febrile illness, i.e. axillary temperature of <37.5 °C ).
• Axillary temperature of ≥ 37.5 °C at the time of vaccination.
• Any clinically significant abnormal finding on screening from biochemistry or haematology at 19 weeks.
• History of allergic disease or reactions likely to be exacerbated by any component of the vaccine, e.g. egg products.
• Presence of any underlying disease that compromises the diagnosis and evaluation of response to the vaccine.
• Invasive bacterial infections (pneumonia, meningitis).
• Any other on-going chronic illness requiring hospital specialist supervision.
• Administration of immunoglobulins and/or any blood products within one month preceding the planned administration of the vaccine candidate.
• Any history of anaphylaxis in reaction to vaccination.
• Research physician's assessment of lack of willingness by parents to participate and comply with all requirements of the protocol, or identification of any factor felt to significantly increase the infant's risk of suffering an adverse outcome.
• Likelihood of travel away from the study area.
• Untreated malaria infection.
• Any other clinical evidence of infection.