Thai HIV Vaccine Trial Results Called "Weak"

Martha Kerr

October 14, 2009

October 14, 2009 — Results of a prime-boost HIV vaccine clinical trial conducted in Thailand were released September 24 by the National Institutes of Health and, as reported by Medscape HIV/AIDS at the time, showed the vaccine to be safe and 31% effective in the prevention of HIV infection in more than 16,000 adults compared with no vaccine.

Although the researchers admitted the results were not robust, the New York Times reports that 2 published accounts, one on Science magazine's Web site on October 5 and the other by the Wall Street Journal on October 10, cite anonymous AIDS researchers who were given confidential briefings about the trial results. These anonymous sources say that the data "may be even weaker than the authors admitted."

The researchers say that instead of the vaccine being 31% effective, its efficacy may be closer to 26%.

Defending the trial results, Anthony S. Fauci, MD, director of the National Institute of Health's National Institute of Allergy and Infectious Diseases, which financed the trial, said the analysis released on September 24, which included every participant in the trial, was "the gold standard," although he acknowledged that different analyses of the data could show a weaker effect.

Putting several biostatistical analyses in a news release "would have confused everybody," Dr. Fauci said in the New York Times article. He called assertions that the researchers hiding or falsifying data "absurd."

"They couldn't be that stupid," he is quoted as saying. "They were already planning to give confidential briefings to experts. They were about to publish everything in a journal. And they were heading to Paris in 3 weeks to present the results to the world."

More Clarity Needed

"The bottom line is that this makes what was already a borderline result seem even more marginal," Paul E. Sax, MD, clinical director of the HIV Program and Division of Infectious Diseases at Brigham and Women's Hospital and associate professor of medicine at Harvard Medical School in Boston, Massachusetts, told Medscape HIV/AIDS. "We'll have to hope there's more clarity when the study results are presented in a scientific conference and (even better), published in a peer-reviewed journal."

As Dr. Sax wrote in his blog on Monday, "Researchers from the U.S. Army and Thailand announced last month they had found the first vaccine that provided some protection against HIV. But a second analysis of the $105 million study, not disclosed publicly, suggests the results may have been a fluke, according to AIDS scientists who have seen it."

Dr. Sax continued, "In short, two additional analyses (modified per protocol and per protocol) do not show a statistically significant protective effect. In other words, the study subjects who followed the protocol most closely had less protection from the vaccine strategy."

Under the best of circumstances the results are statistically significant, the Harvard researcher said, but he adds that they may not be clinically significant.

"When you add how cumbersome this vaccine is to administer (and probably to manufacture), as well as these new findings, the likelihood of this vaccine strategy making its way to clinical use seems vanishingly small," Dr. Sax observed.

More information about the Thai HIV vaccine trial is available at

Dr. Sax has disclosed no relevant financial relationships.