Researchers are developing a new vaccine for malaria that could be out in the market in six years, US scientists here said.

The new "irradiated sporozoite vaccine" is being developed by a team of scientists at the US-based research institute Sanaria in Rockville, Maryland.

"Malarial vaccinations are required by different types of people. There are those who live in the highly-prone African and South Asian countries, including India, and then we also have the travellers from the less immune places who constitute a sizeable 10 million approximately a year," Stephen L. Hoffman, head of the research team, told.

Hoffman was in town to attend the 92nd Indian Science Congress here.

Malaria, according to the 2003 WHO Report, kills over two million people annually worldwide. It is caused by the parasite plasmodium carried by mosquitoes.

India, which records a large number of malaria cases, is currently on the lookout for a new medicine since the parasite has already started resisting the much-used chloroquinine.

To prepare the vaccine, the plasmodium in its sporozoite stage would be artificially injected into mosquitoes. They would be allowed to continue their lifecycle till a particular stage. They would then be injected into humans in three doses.

According to Hoffman, it has been observed that people living in malaria-prone regions developed a natural immunity to the disease.

"In West Africa, which is very highly prone to malaria, a person who lived for three years without contracting malaria, would never get the disease.

"In Gambia, not as severely affected, the period was found to be approximately nine years," said Hoffman, who has done extensive studies on malaria in Africa.

According to him, there are currently over 70 approaches to producing a malarial vaccine, such as synthetic peptides, recombinant proteins and DNA vaccines. But none of these show signs of coming out in 10 years, he said.

The irradiated sporozoite vaccine has been experimented on a limited number of 14 respondents at the Sanaria lab, and 13 out of them were found to be entirely protected from the disease.

As many as 83 percent were able to survive a second re-challenging (by re-introducing the parasite), Hoffman said.

The vaccine that is headed for intensive studies in the US for another two years would then go into a trial period in Africa as well.