The United Nations Program on HIV/AIDS has backed Thailand's decision to go ahead

with a large scale trial of an experimental AIDS vaccine.

The trial of the American-developed vaccine will involve 2,500 volunteers who are

drawn from at-risk groups, but predominantly intravenous drug users. At the same

time a 5000 person trial in America is underway involving people at risk of contracting

the disease sexually.

AIDVAX is the first AIDS vaccine to be used in widespread trials. Initial tests have

found that it is safe for users and prompts an immune response.

Dr Peter Pilot from UNAIDS said that it was currently estimated that 16,000 people

become infected with the disease each day - most of them in the developing world.

The results of the trial are expected to take 2-3 years to come through.