The trials being conducted at the University of Oxford's Jenner Institute are being led by Professor Adrian Hill.

Malaria is one of the world's deadliest killers, and researchers said the most deadly strain is P. falciparum, responsible for 80 percent of malaria infections and 90 percent of deaths. No vaccine exists against the strain since the parasites responsible for infection live inside cells, where they can't be reached by antibodies.

The vaccine being researched uses a genetically modified chimpanzee adenovirus to produce the malaria antigen and to stimulate a response to the vaccine. But because human adenoviruses -- including the common cold and gastroenteritis -- are widespread, most people have developed some immunity toward them, Hill said. Using a chimpanzee adenovirus ensures a recipient is unlikely to have resistance to that component of the vaccine.

Since the active component of the adenovirus is removed, there is no danger of transmission to the human of the original chimpanzee virus, the scientists said.

The research is being funded by the Wellcome Trust.