The world's largest-ever malaria vaccine trial is being undertaken in seven African countries by GlaxoSmithKline (GSK).
A pivotal efficacy trial of the GSK Biologicals RTS,S is expected to involved up to 16,000 children, with more than 5,000 children already enrolled.
Researchers announced at the fifth multilateral initiative on malaria, pan-African malaria conference that the trial was underway in Burkino Faso, Gabon, Ghana, Kenya, Malawi, Mozambique and Tanzania.
RTS,S is the first malaria vaccine candidate to demonstrate significant efficacy during early development to warrant Phase III testing, GSK said.
Recent Phase II studies by GSK have found that RTS,S reduces clinical episodes of malaria by 53% over an eight-month follow-up period.
Malaria kills more than 800,000 people every year in Africa, the majority of which are under five years old.
GSK Biologicals co-inventor of RTS,S and vice-president of R&D, vaccines for emerging diseases and HIV Dr Joe Cohen said the Phase III trial was a huge undertaking that depended on effective coordination between many stakeholders.
"This is a tremendous moment in the fight against malaria and the culmination of more than two decades of research, including ten years of clinical trials in Africa," he said.