Efficacy, Safety and Immunogenicity Study of GSK Biologicals' Candidate Malaria Vaccine (SB257049) Evaluating Schedules With or With-out Fractional Doses, Early Dose 4 and Yearly Doses, in Children 5-17 Months of Age

The study intends to establish proof of concept for a fractional dose schedule under conditions of natural exposure in children 5-17 months old at first vaccination. The study also aims to establish the role of third dose spacing in a fractional dose schedule, describe the effect of an earlier full fourth dose at Month 14 and describe the effect of multiple fractional or full yearly doses.