Vaccine cuts HIV risk by one-third

SCIENTISTS have for the first time succeeded in protecting people from HIV infection by means of a vaccine, a development that has stunned researchers worldwide and transformed prospects for combating the deadly virus.

The experimental vaccine cut the risk of becoming infected with HIV by 31 per cent, according to results released from the world's largest AIDS vaccine trial of more than 16,000 volunteers in Thailand.

Although the degree of protection is substantially less than would normally be considered enough to warrant rolling out a vaccine, the result has enthused researchers still demoralised over a succession of recent calamitous failures.

One trial of a previous vaccine even appeared to make people who were inoculated with it more, rather than less, likely to become infected with HIV, a result that dumbfounded experts and left some questioning whether an HIV vaccine would ever be possible.

Announcing the latest results yesterday, Colonel Jerome Kim, who helped lead the study for the US Army, said it was "the first evidence that we could have a safe and effective preventive vaccine".

The trial of the vaccine -- in fact, a combination of two earlier test vaccines that had each failed to protect patients when tested separately in earlier trials -- was sponsored by the US Army and the National Institute of Allergy and Infectious Diseases.

The institute's director, Anthony Fauci, warned that this was "not the end of the road", but said he was surprised and very pleased by the outcome.

"It gives me cautious optimism about the possibility of improving this result" and developing a more effective AIDS vaccine, Dr Fauci said.

Even a marginally helpful vaccine could have a big impact. Every day, 7500 people worldwide are newly infected with HIV; two million died of AIDS in 2007, the UN agency UNAIDS estimates.

Australian experts also welcomed the development. John Kaldor, professor of epidemiology at the National Centre in HIV Epidemiology and Clinical Research at the University of NSW, said the finding was "extremely significant".

"A 30 per cent protection rate is on the low side of efficacy that would make a vaccine helpful from a public health point of view," Professor Kaldor said.

"From a perspective of understanding the science of how to prevent HIV infection by immunological means, this must be considered to be a very important finding."

He said the trial result was "the first step along the way to showing that a vaccine strategy can work". As such, he said, it was many times more important than a recent discovery of two broadly neutralising antibodies capable of disabling HIV.

He added that more information would be required before anyone could judge whether the new vaccine deserved to be rolled out to some people, despite its low efficacy rate. That would depend on factors such as how long-lasting the protection was, what the vaccine cost and whether people given the product might negate any protection by behaving in more risky ways.

Details of the $105 million study will be given at a vaccine conference in Paris next month.

This is the third big vaccine trial since 1983. In 2007, Merck & Co stopped a study of its experimental vaccine after seeing it did not prevent HIV infection. Later analysis suggested the vaccine might even raise the risk of infection in certain men. The vaccine itself did not cause infection.