Indian and American scientists say the vaccine has been successfully used in rabbits.

Malaria kills up to three million people a year - mostly children and pregnant women.

Ninety per cent of the 500 million annual cases occur in Africa.

Disguise

Scientists have traditionally found it difficult to develop an effective vaccine because the parasite that causes the disease is highly complex and a master of disguise.

But researchers at the US Centres for Disease Control and Prevention and the National Institute of Immunology in New Delhi say their vaccine "strongly inhibited" the parasite from replicating in the body.

It has been synthesized out of parts of genes which have provided natural immunity against malaria in some people.

Rabbits injected with the vaccine at three-week intervals over a three-month period produced antibodies against the parasite.

Writing in the Proceedings of the National Academy of Sciences, the researchers say: "The results of this study ar encouraging and provide a promising candidate for both travellers who are non-immune and people living in malarious regions of the world."

Mosquito

The malaria parasite is carried by mosquitos. It is pushed into the body and travels to the liver where it changes structure.

It then returns to the bloodstream where it attacks red blood cells.

It continually changes its protein coat so that it can easily slip through the body's immune system defence.

The researchers now plan tests on non-human primates and then on humans.