We're pretty hopeful the vaccine will be effective at preventing malaria

Professor Adrian Hill, Oxford University

Professor Adrian Hill, from the university's department of medicine, said the vaccine, based on fragments of the malaria parasite's own DNA, was the first to target the disease once it had entered the body's cells.

Previous vaccines against the disease, which is responsible for a quarter of all child deaths in Africa, have only been able to attack the parasite before it enters cells.

"Instead of using the malaria parasite itself, inactivated in some way, we are actually using DNA, the genetic material," Professor Hill told the BBC.

"We are using a purified preparation of DNA, which is a gene, and that gene makes a tiny part of the malaria parasite when it is used as a vaccine."

High fever

The Oxford team says tests of the vaccine on British volunteers deliberately infected with malaria have already been undertaken.

Professor Hill said if the Gambia trials were also a success, the vaccine could become available within five to 10 years.

"We're pretty hopeful that we will see the same in the Gambia and that the vaccine will be effective at preventing malaria," he said.

Trials co-ordinator Dr Vasee Moorthy said: "Unless a vaccine is developed, cases of malaria and deaths from malaria will continue to increase over the next few years and will spread to parts of southern Europe and America, from which it had been eradicated."

Malaria kills up to two million people each year. Over 90% of deaths are in Africa and two-thirds are among children.

The mosquito-borne disease causes high fever, muscle stiffness and sweating. It is the most prevalent tropical disease in the world.

More than 40% of the world's population live in countries where malaria is endemic.

Drugs are used to treat victims but climate change, social instability and increased resistance to pesticides and treatments have hampered the battle against the illness.