SCIENTISTS ANNOUNCED the news yesterday that many had all but given up hope of hearing: a drug trial in Thailand had shown that an experimental vaccine could protect against HIV/Aids, even if only to a limited extent.
Few expected the Thai trial to succeed, following more than a decade of disappointment in the search for a vaccine culminating in the failure two years ago of a product made by drug firm Merck which looked much more promising. But in a surprise outcome, the Thai trial, conducted by the US army and Thai ministry of public health, found that a combination of two drugs afforded a 31 per cent protection against HIV infection.
The result was even more surprising as the two vaccines used in combination, Alvac and AidsVax, had not proven effective on their own. AidsVax flopped in trials in the US and also when it was given to 2,500 drug users at risk of HIV infection in Thailand.
Of the 16,000 male and female HIV-negative volunteers who took part in the biggest yet Aids vaccine trial, half were randomly assigned the combined vaccine and the other half a dummy injection.
All participants had been counselled about protecting themselves and given condoms and treatment for sexually transmitted infections to reduce their chances of picking up the virus. Of the first group, 51 were infected. Of the second, 74 became HIV positive.
The reaction from Aids scientists and campaigners came like a shriek of joy. “This is the first HIV vaccine candidate to successfully reduce the risk of HIV infection in humans,” said Lieut Gen Eric Schoomaker, the US army’s surgeon general. “We are very excited and pleased with the outcome of this trial and congratulate all those who participated in it.”
“This is a historic day in the 26-year quest to develop an Aids vaccine,” said Dr Alan Bernstein, executive director of the Global HIV Vaccine Enterprise, an alliance of research organisations.
Warren Mitchell, executive director of the Aids Vaccine Advocacy Coalition, called it a historic milestone. But all recognised the enormous amount still to do if a promising trial result is to be turned into a routine vaccination.
Dr Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases, which part-funded the trial, said he was surprised and pleased by the outcome, but warned it was “not the end of the road”.
The trial has shown evidence that a “prime boost strategy”, one vaccine followed later by the other, using two vaccines made of synthetic fragments of HIV based on subtypes B (common in the US and Europe) and E (common in Thailand and southeast Asia) can work. The full results will be presented at an Aids vaccine conference in Paris next month.
The next steps are more analysis, research and trials. If efficacy had reached more than 50 per cent, it would have been submitted to Thai authorities for a licence.
There is some way to go yet, and much to do if the approach is to be adapted to make a vaccine that works in Africa, where the strain is different. – ( Guardianservice)