VaxGen Results May Be Statistically ‘Weaker’ Than Originally Reported
Officials at Brisbane, Calif.-based VaxGen yesterday said that statistical evidence about the effectiveness of its experimental AIDS vaccine AIDSVAX may be "weaker" than initially thought, the Wall Street Journal reports (Wall Street Journal, 2/27). VaxGen on Monday announced that AIDSVAX reduced the rate of new HIV infections by only 3.8% among people who received the vaccine, compared with clinical trial participants who received a placebo injection, but said that it was effective among African Americans, Asians and other non-white, non-Hispanic volunteers. The study consisted of 5,108 gay or bisexual men and 309 women who were HIV-negative when they began the trial, but at high risk for HIV infection because they had sex partners who injected drugs or had sex with men. About twice as many people were randomly assigned to receive injections of the vaccine than were assigned to the placebo group (Kaiser Daily HIV/AIDS Report, 2/24). VaxGen said that in a subgroup of 498 non-white, non-Hispanic volunteers the vaccine "appeared to provide protection in the range of 30% to 84%," the Journal reports. According to the company, the analysis had less than a 1% chance of being random chance, making it statistically significant. But the analysis has been "criticized" by outside scientists because it is based on only 29 HIV infections among vaccinated participants in that subgroup and those who received a placebo, according to the Journal. Although the company originally said that it took "penalties" to reduce the statistical significance of results obtained from parsing out a large set of data, Lance Ignon, vice president for communications at VaxGen, said yesterday that the company did not take such penalties (Wall Street Journal, 2/27). Steven Self, a professor of biostatistics at the University of Washington who VaxGen consulted, said, "It's probably an honest error"; however, he added that the fact that the lower bound of the confidence interval was above zero provided "some marginal statistical evidence that there is some efficacy in that subgroup" (Pollack, New York Times/San Francisco Chronicle, 2/27). VaxGen CEO Lance Gordon yesterday told the CDC Advisory Committee on Immunization Practices in Atlanta that the results are still "preliminary," USA Today reports. Company scientists had just a week to comb through data, and a "full analysis is still in progress," with more information to be released next month, he said (USA Today, 2/27).This is part of the KHN Morning Briefing, a summary of health policy coverage from major news organizations. Sign up for an email subscription.