he coast could be beyond the reach of many countries and its efficacy will probably be limited, but researchers are optimistic that a vaccine for HIV/AIDS will be available within 10 years, a US health expert has said.

Dozens of vaccine prototypes are under development around the world. With some 9,000 people participating in clinical trials, said Margaret Johnston, Associate Director of AIDS vaccines at the National Institutes of Health in the US. "There's never been more optimism than there is now that an HIV vaccine can be identified," Johnston told delegates at the 6 th International Congress on AIDS in Asia and the Pacific in Melbourne.

"However, we don't know what it will look like just yet. We don't know how it will act. Clinical trials will take a long time and it's likely the first (vaccines). will not be 100 per cent effective," she added.

The product being developed is made from a protein that forms on the outer surface of the HIV virus and stimulates antibodies to neutralize or stop the virus from spreading.

Now being tested in Thailand, North America and the Netherlands, results could be available as early as next month.

If they are promising, another larger trial over 3 years would be conducted, she said.

Johnston said it was anticipated a future vaccine would protect people from contracting HIV/AIDS and when given to those who already have the virus, prevent its spread.

Production costs and pricing were difficult to estimate she said.

Costs would be increased by the need to license and buy patent rights, while manufacturing coasts would depend on the vaccine design, Johnston said.

"For example, a DNA-based vaccine might be mass-produced at a cost of pennies to dollars per does. But a (more complex) vaccine that requires a more high tech approach to manufacturing will likely cost tens of dollars if not 100 dollars or more to produce," she added. -AP