Double-blind Study of Safety and Immunogenicity of Two Candidate Malaria Vaccines in Gabonese Children

Inclusion criteria: * A male or female child between 18 months and 4 years of age (up to but not including 5th birthday) at the time of first vaccination. * Written or oral, signed or thumb-printed and witnessed informed consent obtained from the parent(s)/guardian(s) of the child. * Subjects who the investigator believes that their parents/guardians can and will comply with the requirements of the protocol (e.g. return for follow-up visits) Exclusion criteria: * Acute disease at the time of enrolment. * Serious acute or chronic illness determined by clinical or physical examination and laboratory screening tests. * Laboratory screening tests for haemoglobin, total white cell count, platelets, ALT and creatinine out of range. * Planned administration/administration of a vaccine not foreseen by the study protocol within 30 days of the first dose of vaccine(s) with the exception of tetanus toxoid. * Use of any investigational or non-registered drug or vaccine within 30 days preceding the first dose of study vaccine, or planned use during the study period. * Administration of immunoglobulins, blood transfusions or other blood products within the three months preceding the first dose of study vaccine or planned administration during the study period. * Chronic administration of immunosuppressants or other immune-modifying drugs within six months prior to the first vaccine dose. * Previous participation in any other malaria vaccine trial. * Simultaneous participation in any other clinical trial. * Same sex twin. * History of allergic reactions (significant IgE-mediated events) or anaphylaxis to previous immunizations. * History of allergic disease or reactions likely to be exacerbated by any component of the vaccine. * Any other findings that the investigator feels would increase the risk of having an adverse outcome from participation in the trial.