The world's largest HIV/Aids vaccine trial - conducted in Thailand over the last several years - shows that it's now possible to produce a powerful prevention against the viral killer.

"The outcome represents a breakthrough in HIV vaccine development because for the first time ever there is evidence that an HIV vaccine can be effective," Thailand's Public Health Minister Witthaya Kaewparadai said yesterday (September 24).

However, while the Phase III trial, carried out jointly by the US military and Thai scientists, found that the experimental vaccine is 31.2 per cent effective in reducing the risk of infection, it failed to reduce the HIV virus in the blood of infected persons.

Dr Suppachai RerkNgam, project director for Thailand's Phase III HIV vaccine clinical trial, said researchers aimed to achieve a 50 per cent efficacy rate, but the outcome was less at 31.2 per cent.

"Although it's not high enough for use just yet, this is significant evidence that can lead to higher vaccine efficacy in the future. Whether the vaccine will be licensed, or what further studies need to be done, will be considered thoroughly by Thai and international experts," he said.

Colonel Jerome Kim of the US military's HIV research programme said via a video link that there could be an effective vaccine in the near future.

"This was a turning point for the perspective of vaccine research," he said. "I believe that from now scientists around the world will convene and discuss among each other on how to develop the next generation of HIV vaccine in the future."

The Thai experiment, known as RV 144, tested the "primeboost" combination of two vaccines: ALVAC HIV vaccine (the prime) produced by SanofiPasteur, and AIDSVAX B/E vaccine (the boost) produced by the Global Solutions for Infectious Diseases.

This combination was based on an HIV strain that commonly circulates in Thailand.

The RV 144 was designed to test the vaccine strategy's ability to prevent HIV infection, as well as its ability to reduce the amount of HIV in the blood (viral load) of those who became infected after they enrolled in the study.

The Public Health Ministry conducted the study, which was sponsored by the US Army Surgeon General with US$105 million (3.5 billion baht), while Mahidol University and the Armed Forced Research Institute of Medical Science, operating out of Thailand, helped to conduct the trial.

The Phase III vaccine study was launched in 2003 and involved 16,402 noninfected volunteers aged between 1830 years, at average risk of HIV infection. Half of them received the primeboost vaccine combination and half received a placebo.

The vaccinations ended in July 2006, and the volunteers took a HIV test every six months for three years.

They received counselling on how to prevent infection with HIV at the beginning of the study and every six months after the start of the trial, for a total of three and a half years.

The International Data and Safety Monitoring Board did not identify any safety concerns after they met eight times since the trial's inception.

The study vaccines did not cause HIV infection because they are not made from and do not contain the entire virus, either live or killed.

-The Nation/Asia News Network