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The new vaccine that reduces HIV/AIDS infection rates is the first of its kind in the world. Its inventors have now explained the details of their trial results at a Paris congress.
Over 30 million people around the world are infected with HIV/AIDS
The large-scale AIDS vaccine trial in Thailand made news around the world, showing a 31.2-percent lower infection rate among people who received a combination of shots.
The US-funded study on 16,402 volunteers is a breakthrough in vaccine development for HIV/AIDS.
The doctors behind the study have now released details of their findings and said careful review showed that they held up. At a conference in Paris, Supachai Rerks-Ngam, the researcher at the Thai health ministry responsible for the medical trial, on Tuesday declared that "it is now possible to develop a vaccine against AIDS."
The vaccine discovery was first revealed to the public in September. At a press conference in Bangkok, Thai Health Minister Witthaya Kaewparadai described the outcome of the six-year study by US and Thai researchers as a positive step forward in the search for an HIV/AIDS vaccine.
Since the disease emerged in the early 1980s, progress has been made in containing and treating the disease, but up to now there has been no sign of a vaccine or cure.
Thai Health Minister Witthaya Kaewparadai gave details of the study
In the study, half of the volunteers - heterosexuals with no special risk of AIDS infection - were given a placebo. The other half were given a combination of two vaccine shots - Alvac and AidsVax - which had failed to show effectiveness when given individually.
Sanofi-Pasteur's Alvac is a disabled canary pox vaccine that smuggles HIV genes into the body and encourages the production of protective T-cells. AidsVax, currently owned by the non-profit Global Solutions for Infectious Diseases, contains a recombinant protein aimed at stimulating a significant antibody response against the HIV protein.
The study represents a revival in a campaign to find a vaccine that appeared to stall just two years ago, when use of Merck's experimental Ad5 vaccine boosted some people's chances of infection in a study.
The result of the current study was almost completely unexpected, and researchers said they couldn't figure out why the two-pronged attack of immune system vaccines was working.
But it was a triumph for the trial's supporters, who carried out the controversial study despite severe criticism.
"Myself, like others, did not think there was a very high chance that this would give any degree of efficacy," Anthony Fauci of the US National Institute of Allergy and Infectious Diseases, which helped fund the study, told Reuters.
Subjects in the trial were given four doses of the Alvac vaccine and two of the AidsVax shot over six months, then monitored for three years. They were also given advice on safe sex. There were no serious side effects, the researchers said.
Not a world-wide cure
Of those who received the vaccine, 51 became infected with HIV, compared with 74 who received a placebo. Those in the study who became infected during the trial were given free access to treatment, researchers said.
Although only a small number of people were affected in the trial overall, the numbers are nonetheless statistically significant, said Adriano Boasso, an HIV vaccine expert in London.
Tests will have been done to verify that the difference is unlikely to have occurred by chance and I have no trouble believing the figures," Boasso told BBC news.
The vaccine trial doesn't indicate that a worldwide cure is around the corner. Jerome Kim, a deputy director of science at the Maryland-based Walter Reed Army Institute of Research, which sponsored the trial, stressed that the vaccine may not work in the people and places where HIV is most common - in Africa, among men who have sex with men, and among injecting drug users.
"The vaccine was tested in Thailand and it is really specific for the strains that are circulating in Thailand now," he said.
But he stressed the importance of the trial, saying that, "although the results were modest … (the study) gives us hope that a globally effective HIV vaccine may be possible in the future."
The vaccine is a step forward in the fight against AIDS
Mitchell Warren, director of the New York-based AIDS Vaccine Advocacy Coalition, stressed the positive implications of the results in an interview with Bloomberg news service.
"Wow," said Warren, whose group was not involved with the study. "We are in a new place in the search for an AIDS vaccine. It's safe to say that the scientific community is caught off-guard."
The two main United Nations agencies dealing with HIV/AIDS, the World Health Organization and the UNAIDS agency, also said they were "optimistic" about the "encouraging" results.
The agencies noted that it may not be possible to get licensing permission for the drug at the moment based on the limited results, and that further studies would have to be done to determine if the vaccine has the same effect in other parts of the world.
Editor: Kate Bowen