PARIS—Researchers who last month touted the potential breakthrough represented by an experimental vaccine for AIDS admitted Tuesday the results of a recent three-year clinical trial are not as encouraging as they initially thought. However, although subsequent analysis of the results falls short of statistical significance, researchers remain convinced the work eventually will lead to an effective AIDS-prevention inoculation regimen.
Conducted at clinics in Thailand by the U.S. Army, the Royal Thai Army and Thailand’s Ministry of Public Health, the experiment’s initial results—made public in late September in a press release—seemed to demonstrate the first-ever small, but statistically measurable, ability to reduce a person’s risk of becoming infected with HIV-AIDS. According to the Army’s surgeon general, a complicated series of primary and booster vaccinations was safe and 31 percent effective in preventing HIV infection. A paper released Tuesday during a scientific conference in Paris, however, revealed the regimen provided no protection to subjects at highest risk of contracting the disease. For those in lower-risk categories, protection declined over the first year after they completed the series of six shots.
Nevertheless, AIDS researchers said the study provided important incremental data that can help direct future endeavors.
“This is a modest effect at best, but I believe it has relevance and is a real effect that needs to be built upon,” National Institute of Allergy and Infectious Diseases Director Anthony S. Fauci told The Washington Post. The institute provided much of the study’s $105 million funding.
Others within and without the scientific community worry “hyping” of early, improperly analyzed results may have done irreparable damage to the credibility of future research.
“When this was rolled out a couple of weeks ago, it was terribly hyped by the investigators,” Gregg Gonsalves, an AIDS activist for two decades, told the Post. “Some people think you have to dangle the slimmest morsels of hope in front of the general public in order to keep them interested in an AIDS vaccine, but I think that damages the credibility of the effort.”
The change in the way the study results are viewed was introduced by differences in statistical methods, not in the results themselves, researchers were quick to point out. The initial evaluation was based on a preliminary analysis of effects across the entire sample of 16,402 male and female Thai volunteers, random halves of whom received either a placebo or the investigational vaccines. Only 132 of the subjects became infected during the study. When the data was corrected to exclude the control group (placebo recipients) and seven individuals found to have been infected with HIV prior to the start of the investigation, the results lost their statistical significance.
The later analysis, which investigators now admit was accomplished in a more widely accepted scientific context, was not altogether discouraging, though. Researchers discovered the vaccination regimen was 40-50 percent effective in low- and medium-risk heterosexual subjects and in people who are homosexual or bisexual and monogamous. The experimental program offered little or no protection to those at highest risk of infection, however: non-monogamous subjects of any sexuality, sex-trade workers and drug users who share needles.
The New England Journal of Medicine plans to publish the research findings in an upcoming issue.
