Efficacy, Safety and Immunogenicity Study of GSK Biologicals' Candidate Malaria Vaccine 257049 in the Sporozoite Challenge Model in Healthy Malaria-naïve Adults

This study is designed to evaluate safety, reactogenicity, immunogenicity, and efficacy of GSK Biological's malaria candidate vaccine 257049 administered as standard doses at 0 and 1 months and 1/5th standard dose at 7 months (delayed fractional dose group) and 257049 administered as three standard doses one month apart (0, 1, 2-month group) in healthy malaria-naïve volunteers aged 18-50 years in the sporozoite challenge model. An additional, delayed sporozoite challenge will assess persistence of protection induced by the primary immune schedule and if an additional dose can provide protection in those unprotected by the initial vaccination series.