September 24, 2009
BANGKOK (AFP) - An experimental AIDS vaccine has for the first time cut the risk of infection in a "breakthrough" in the quarter-century battle against the deadly epidemic, researchers said on Thursday.
The vaccine reduced the risk of being infected by almost a third, they said after the world's largest vaccine trial of more than 16,000 volunteers, carried out by the US Army and Thailand's Ministry of Public Health.
"It is the first demonstration that a vaccine against HIV can protect against infection," Colonel Jerome Kim of the US military HIV research programme told a news conference in Bangkok via videolink.
"This is a very important scientific advance and gives us hope that a globally effective vaccine may be possible in the future," he said.
The vaccine was a combination of two older shots that had not reduced infection on their own, and the researchers said they were now studying why the two vaccines apparently worked together.
The study combined the canarypox vaccine ALVAC, manufactured by Sanofi-Aventis of France, and AIDSVAX, originally made by VaxGen Inc and now licensed to Global Solutions for Infectious Diseases.
"The outcome represents a breakthrough in HIV vaccine development because for the first time ever there is evidence that HIV vaccine has preventative efficacy," said a statement released by the researchers.
"The vaccine has a 31.2 percent efficacy in reducing the risk of HIV infection."
It was tested on volunteers -- all HIV negative men and women aged from 18 to 30 -- at average risk of infection in two Thai provinces near Bangkok starting in October 2003.
Half received the vaccine and the rest were given a placebo. Out of the placebo recipients 74 of 8,198 became infected compared with 51 of 8,197 who got the vaccine.
Thai Public Health Minister Witthaya Kaewparadai said the "outcome of this study is a scientific breakthrough."
AIDS first came to public notice in 1981 and has since killed at least 25 million people worldwide, and 33 million others are living with AIDS or the HIV virus.
Swift progress in identifying the virus that caused it unleashed early optimism that a vaccine would quickly emerge. HIV destroys immune cells and exposes the body to opportunistic disease.
But out of the 50 candidates that have been evaluated among humans, only two vaccines have made it through all three phases of trials, and both were flops. About 30 vaccines remain in the pipeline.
US ambassador to Thailand Eric John told the news conference in Bangkok that the vaccine trial had "incredible conclusions and brought us one step closer to an HIV vaccine".
He said more research was needed to find out why the combination of the two previously ineffective vaccines worked, but added that the results had "important implications" for a future vaccine.
Sanofi Pasteur, the vaccines division of Sanofi-Aventis, said the trials were the "first concrete demonstration" that a vaccine "could one day become a reality."
"Although modest, the reduction in risk of infection by HIV is statistically significant," said Michel DeWilde, senior vice president for research and development at Sanofi Pasteur.
In New York, the International AIDS Vaccine Initiative (IAVI), an organisation that promotes the search for a vaccine, said the trial results were "very exciting and a significant scientific achievement."
"It's the first demonstration that a candidate AIDS vaccine provides benefit in humans. Until now, we've had evidence of feasibility for an AIDS vaccine in animal models," IAVI president Seth Berkley said in a statement.
Earlier this month in a study published in the journal Science, US researchers said they had discovered two powerful new antibodies which could hold the key to achieving a viable AIDS vaccine.
