Doctors who surprised the world of AIDS research with a study showing a vaccine prevented some HIV infections released details of their findings on Tuesday and said careful review showed they held up.
Full details of the study, which showed the experimental vaccine prevented nearly one-third of infections among 16,000 ordinary Thai volunteers, were published in the New England Journal of Medicine.
That's a validation of the results, said Jerome Kim, a U.S. Army colonel at the Walter Reed Army Institute of Research in Maryland, who helped lead the trial.
The vaccine is a combination of Sanofi-Pasteur's ALVAC canary pox/HIV vaccine and the failed HIV vaccine AIDSVAX, made by a San Francisco company called VaxGen and now owned by the non-profit Global Solutions for Infectious Diseases.
The trial, sponsored by the U.S. government and the Thai Ministry of Public Health, cut the risk of infection by 31.2 percent over three years, according to one analysis of the data.
Kim's team said the effect was modest and hard to interpret, that the vaccine was not nearly ready for commercial use and might not work in Africa, where AIDS is most common.
What worked might have been the combination of both drugs, and not one or the other, Kim told a news conference in Paris on Tuesday after he and colleagues presented the findings to a meeting of AIDS vaccine researchers.
The combination in the vaccine generated slightly different and slightly more potent response than each individual component alone, we don't know that that's the case here, but it's something wewe'dd like to investigate.
Days after the results were announced at an unusual news conference in Bangkok in September, some unidentified researchers were quoted by Science magazine and The Wall Street Journal as saying the study was weaker than at first presented.
At issue were the statistical methods used to analyze the data.
Kim's team conducted three different analyses -- one called an intention to treat analysis, one called a modified intention to treat analysis and one called a pro-protocol analysis.
Those who questioned the findings, according to media reports, said two of the methods were statistically insignificant.
In a commentary in the journal, Raphael Dolin of Beth Israel Deaconess Medical Center and Harvard Medical School in Boston said the study had been rigorously designed and conducted.
Although the merits of each type of analysis can be debated, all three yielded a possible, albeit modest, effect of the vaccine in preventing HIV infection, Dolin wrote.
What is still unclear was how long the protection lasts and how much each of the two vaccines contributed.
The most important thing all of us are interested in is why from a scientific standpoint we saw the results that we saw, U.S. Army Colonel Nelson Michael told Reuters.
The AIDS virus infects an estimated 33 million people globally and has killed 25 million since it was identified in the 1980s. Cocktails of drugs can control HIV but there is no cure. In 2007, Merck & Co ended a trial of its vaccine after it was found not to work, and in 2003, AIDSVAX used alone was found to offer no protection, either.
Supachai Rerks-Ngarm, a disease control expert from Thailand's Health Ministry, said more work would need to be done with trial participants.
We have to explain what made the vaccine work, and how we can make it work better for future improvement of vaccine candidates, he told Reuters.