Scientists believe a chimp virus may hold the clue in the long-running battle to develop a malaria vaccine.
People are infected with malaria from mosquitoes
Experts have been trying for the last 20 years to find a jab for the disease, which kills more than 1m people a year.
An Oxford University team are using the chimp virus to provoke an immune response in cells where the parasites responsible for malaria gather.
Trials are just getting under way and, if they prove successful, a vaccine may be available within five years.
The team is using a genetically-modified chimp adenovirus combined with a malaria gene in a bid to kill the parasites once they enter the body.
Previous research had shown that adenoviruses, which cause common problems such as colds and gastroenteritis, are particularly effective at triggering such an immune response.
But as many people will have been exposed to the human adenovirus the team, funded by the Wellcome Trust, turned to the chimp version.
Lead researcher Dr Sarah Gilbert said: "Chimpanzees have their own set of adenoviruses which rarely infect humans, so we have not built up immunity to them.
"This is why we have chosen such a virus to form the backbone of the new vaccine."
Oxford University is just one of several groups reaching the trial stage with potential vaccines.
The disease has proved a particularly tricky challenge as it is so complex.
Malaria pathogens have thousands of genes compared to the scores in many of the diseases which vaccines have already been developed for.
And the lack of progress has left doctors relying on drug treatments and bed nets to keep away mosquitoes which carry the malaria parasite.
It means promises made in 2000 to halve the burden of the disease within 10 years are almost certainly going to be missed.
However, experts believe significant steps are now being made.
Colin Sutherland, from the London School of Hygiene and Tropical Medicine, said the Oxford University research showed "promise".
He added: "I think we are getting closer with a vaccine and there is more confidence now than there has been for 10 years.
"The problem is that it is so complex and if we do get there it will be one of the biggest vaccine achievements."