A major trial in Thailand of a potential vaccine for HIV has ended in failure. VaxGen, the US-based company that developed the candidate vaccine known as AIDSVAX, announced yesterday (12 November) that it did not prevent HIV infection or slow the progress of the disease.

The results follow preliminary findings released in February that the vaccine did not prevent HIV infection in the United States and Europe, but offered some protection to black and Asian participants (see Mixed results from AIDS vaccine trial)

"The outcome of this trial is one more reminder of how difficult it is to combat HIV and how important it is for the international public health community to redouble the effort to develop an effective vaccine," said Donald Francis, VaxGen's president, in a statement

But despite the disappointing outcome, he said that the trial was a valuable example of how such trials can be conducted. "VaxGen and our Thai collaborators have created a model that can be used around the world for advanced clinical research of an HIV vaccine," he said.

More than 2,500 injecting drug users in Bangkok were involved in the three-year trial. Half of the participants were given injections of the candidate vaccine, and the other half were given a placebo. During the trial, 105 volunteers given the placebo became infected with HIV, compared to 106 volunteers who had received the vaccine.

The failure of the trials is a major setback to Thailand's fight against HIV/AIDS. Early last month, the Thai government launched a US$25 million programme to provide free antiretroviral drugs for its 50,000 HIV/AIDS population.

Kachit Choopanya, the trial's principal investigator, said in a statement that despite its failure, the study shows Thailand's commitment to HIV vaccine development. "With the help of the trial volunteers and national and international collaborators, Thailand has strengthened its research capacity and acquired valuable expertise with which to carry on clinical research," he said.