Let's go for human testing of vaccine, says UNAIDS.

• Position: Programme on HIV/AIDS

The Joint United Nations Programme on HIV/AIDS (UNAIDS) has expressed its support to the decision by Thailand's Ministry of Public Health to authorize large-scale human testing of an experimental AIDS vaccine, the first such trial in the developing world. "This trial signifies an important early step toward the development of a safe and effective vaccine against HIV, an essential strategy for bringing the epidemic under control", said Dr. Peter Piot, Executive Director of UNAIDS. "At this point, we cannot fully predict this vaccine's potential for protecting people against HIV. This trial will provide important information that can help us understand how this and other AIDS vaccines may work and how to improve their efficacy ... (and) will help build the foundation for future vaccine clinical trials in the developing world."

Many experts agree that in order to accelerate AIDS vaccine development, different types of vaccines must be tested in parallel. These multiple trials will need to be conducted in developed and developing countries to test the efficacy of these vaccines against different HIV strains in different populations worldwide. The trial in Thailand will test the AIDSVAX vaccine, developed by VaxGen, Inc., of California, which began a large-scale trial in the United States last June. The vaccine will differ from the product tested in the United States, to match the different strains of HIV that exist in Thailand. The Thai trial will involve 2,500 volunteers who are at higher risk for HIV infection because of injecting drug use; the United States trial involves 5,000 volunteers primarily at risk through sexual transmission.

AIDSVAX is not the first experimental AIDS vaccine, or vaccine candidate, to be tested in humans. Since 1987, a number of vaccine candidates have been given to people enrolled in small clinical trials in the United States, Thailand and other countries. But after having been found to be safe and to stimulate an immune response, AIDSVAX is the first vaccine candidate to proceed to large-scale human testing, known as "Phase III", or efficacy trials. The only way to know if a vaccine is effective in protecting against HIV infection or disease is by conducting large-scale trials in humans; the first results from the AIDSVAX trials will only be available in two to three years.

"Most experts...