Professor Barry J Marshall, the 2005 Nobel Laureate for Physiology or Medicine, said his team was working to develop a vaccine, which would probably be taken orally. He expected their work to be completed in about 10 years.

The team had been studying the bacteria's DNA to try and discover how it could survive in an infected person's stomach for so long. Unlike other bacteria found in the human body that are usually expelled in a matter of weeks, H pylori can remain for up to 15 years, Marshall said.

"So we think H pylori understands the human system very well and is controlling the body's white blood cells and antibodies so as not to be eradicated," he said.

"If we can understand how H pylori can control the immune system that will allow us to develop drugs and new kinds of treatment ... and finally we will be able to develop a vaccine," he added.

Though drugs are currently available to treat H pylori infection, they are quite expensive and about 10 per cent of people treated are still not completely cured, Marshall said.

He said scientists must also consider that different countries have different types of H pylori and that different racial groups suffer from the infection in different ways.

If a vaccine is found, Marshall said he would try make it as cheap as possible so it would be affordable to developing countries.

"We don't know yet ... it's an interesting project and hopefully we'll meet with some success," he said.

In addition to being a Nobel Laureate, Marshall also received the 2001 Prince Mahidol Award for Public Health.

Arthit Khwankhom

The Nation