An effective vaccine against malaria has been developed and could be licensed by 2010, scientists say.
The vaccine protected children against malaria
Many other candidate vaccines are in development, but experts say trial results of this one, published in the Lancet, are the most promising yet.
The vaccine was used to protect 2,022 children in Mozambique and cut the risk of developing severe malaria by 58%.
The team, led by a Spanish expert from the University of Barcelona, is working with drug company GlaxoSmithKline.
Lead researcher Professor Pedro Alonso said: "These are clearly the best results we have ever seen with a candidate malaria vaccine.
"We are quite certain not only that the vaccine is safe...but that we have seen a clear efficacy."
The team tested the trial vaccine, called RTS,S/AS02A, on children aged between one and four years old in Mozambique, where malaria is widespread.
Globally, over one million people, many of them children under the age of five, die from malaria each year.
Ninety percent of all malaria cases are in sub-Saharan Africa.
Preventing infection is especially important because resistance to anti-malarial drugs is a growing problem.
The healthy children in the study were randomly allocated to receive three injections of the malaria vaccine or a vaccine against a common childhood disease, such as Hib, which acted as a control.
At six months, the malaria vaccine had reduced a child's risk of developing one episode of malaria by 30%.
The risk of developing severe malaria was reduced by 58%.
The team followed up 400 of the children for longer and found the vaccine extended the time to first infection by 45%.
Professor Alonso said it would have been unrealistic to have expected the vaccine to prevent 100% of infections and that the results were really encouraging.
"It's difficult to imagine that we will have in the near future a magic bullet that by itself can sort out the problem of malaria," he said.
"Just like any other malaria control tool that we have, like insecticide treated nets... none of them is 100% effective.
"Control will rely on using a combination of malaria control tools together.
"We believe a malaria vaccine, even of moderate efficacy, could make a huge impact."
Among the under two year olds in the study, the vaccine was 77% effective against severe malaria.
The scientists said these young children would be the ultimate target group to vaccinate.
Further trials will be needed to prove the vaccine is safe before a licence can be granted, but the researchers are hopeful this will happen by 2010.
It was well-tolerated by the children in the study, with few serious side-effects.
Allan Shapira, of Roll Back Malaria, said: "The research is very high quality and the findings are very encouraging."
He said there would always be concerns about the possible cost and availability of vaccines and treatments for malaria.
How it works
The vaccine is directed against the form of the malaria parasite that is injected by mosquitoes. This form is known as the sporozoite.
After immunization, antibodies and white blood cells are produced which can prevent the sporozoite from surviving or from further development in the liver.
The research was funded by GSK Biologicals and a global project, created through a grant from the Bill & Melinda Gates Foundation, to overcome barriers to malaria vaccine development - the PATH Malaria Vaccine Initiative.
Mozambique's Minister of Health, Dr Francisco Songane, who approved the trial, said: "Malaria is the number one killer of African children.
"We did this not only for the people of Mozambique, but for the people all over Africa whose health and development suffer greatly from this terrible disease."