Doctors say malaria kills up to 2.7 million people worldwide each year and is second only to tuberculosis in its impact on human health.

Those battling to bring the disease under control have long sought a cheap vaccine to prevent its spread.

Now scientists think they can use DNA from a virus to build up strong resistance to the disease.

DNA is the material that carries genetic information.

Strong resistance

A study published in the journal Science found that injecting a virus' DNA into a human would raise levels of immune cells in the blood stream.

This gave the test subjects much greater resistance to disease.

The disease is transmitted by mosquitoes

Although the scientists were only testing the DNA vaccine to see if it would provoke any sort of immune response, the level of resistance achieved was strong enough to fight several varieties of malaria.

The research was conducted by Dr Stephen Hoffman, director of the Malaria Programme at the US Naval Medical Research Institute.

Dr Hoffman said the new type of vaccine prompts cells in the body to use the foreign DNA information to produce a neutralised strain of the virus.

This enables the body to recognise and fight an infectious strain of the virus if it invades, he said.

Production problems

The World Health Organisation estimates there are 300 million to 500 million cases of malaria each year.

More than 90% of them are in Africa, where the disease is the biggest killer on the continent.

Mosquitoes with parasites in their bellies pass the disease on to humans through their saliva.

Traditional vaccines are expensive and take a long time to produce. They use full-grown but weakened strands of a virus to stimulate the body's immune response.

Dr Hoffman said that DNA-based vaccines are easier and cheaper to produce.

"Any molecular biology laboratory in the world can make DNA vaccine and make it quite rapidly," he said.

Stable vaccine

DNA vaccines are much more stable, allowing them to be easily transported, especially to poorer countries without advanced laboratory facilities, he said.

Another benefit of DNA vaccination, Dr Hoffman said, was that traditional live vaccines, such as the polio vaccine, can in rare cases cause people to contract the disease they were trying to prevent.

He said: "With a live vaccine, there is always a danger of it reverting and becoming infective. DNA cannot become infective."

Because of the success so far, the scientists hope to start tests to see if the vaccine can protect humans from malaria next summer.

Malaria cannot be caught in the UK, but people sometimes bring the disease into the country when they return from trips abroad.

Last year there were 1,476 suspected cases of malaria in the UK.