VaxGen AIDS Vaccine ‘Largely Ineffective’ at Reducing HIV Infection Rate; African Americans, Asians Show Stronger Protective Effect
Brisbane, Calif.-based biotech firm VaxGen today announced that its experimental AIDS vaccine only 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, proving the vaccine to be "largely ineffective," the Washington Post reports. However, the vaccine appeared to be more effective among African Americans, Asians and other non-white, non-Hispanic volunteers (Brown, Washington Post, 2/24). The vaccine, called AIDSVAX, mimicks the protein gp120, which resides on the outer surface of the HIV molecule. By introducing a portion of the protein into the body, researchers hoped to stimulate an immune response in vaccine recipients (Kaiser Daily HIV/AIDS Report, 10/24/01). The study consisted of 5,108 gay or bisexual men and 309 women who were at high risk for HIV infection because they had sex partners who injected drugs or had sex with men, and all of the participants received constant counseling on how to prevent HIV infection and were told not to rely on the vaccine to protect them from infection. All of the participants were HIV-negative when they began the study. About twice as many people were randomly assigned to receive injections of the vaccine than were assigned to the placebo group, and participants were recruited to trial locations in the United States, Canada, Puerto Rico and the Netherlands. The vaccination schedule included three shots every three months, followed by booster shots every six months. According to the Post, the analyzed data only included the 5,009 participants who received at least three shots (Washington Post, 2/24).
Overall, 5.7% of participants who received the vaccine tested HIV-positive during the three years of the trial, compared to 5.8% of the people who received the placebo. That difference was not statistically significant, meaning that the results could be due to chance (Pollack/Altman, New York Times, 2/24). However, the rate of infection among African Americans, Asians and other non-white, non-Hispanic minorities who received the vaccine was 3.7%, compared with 9.9% in the placebo group. After "some statistical adjustments," researchers determined that the vaccine lowered the infection rate in this group by 66.8%, a statistically significant result, the New York Times reports (Pollack/Altman, New York Times, 2/24). Vaccines are usually required to be a minimum of 70% effective in preventing new infections to receive approval for widespread use, the Post reports. "It appears that blacks, Asians and the other non-white [non-Hispanic] volunteers were able to induce a higher level of antibody than others," VaxGen spokesperson James Key said (Washington Post, 2/24). Researchers said that the results among African-American participants were "totally unexpected," according to the Times. The researchers also said that minorities made up only a "small fraction" of trial participants and the results could change if the vaccine was "tested among more members of minorities" (New York Times, 2/24). VaxGen said that it plans to conduct more studies "to confirm if there was a direct correlation between the level of antibodies and the prevention of infection" (Abate, San Francisco Chronicle, 2/24).
Jose Esparza, director of AIDS vaccine research for UNAIDS, said that the trial results were "probably the most important accomplishment in vaccine research in 15 years," adding, "This is the first time anyone has shown protection (against HIV) in humans. ... The results tell us that a vaccine can protect humans against HIV." Esparza said that the results among African Americans could "have worldwide ramifications" (Sternberg, USA Today, 2/24). Seth Berkley, president and CEO of the International AIDS Vaccine Initiative, said that the findings were "disappointing," but added, "We are not discouraged. The search for an AIDS vaccine will and must go on" (BBC News, 2/24). "Alternative AIDS vaccines, employing different design strategies, are now in development, and some have already entered human trials. These must move forward through further study, without delay," Berkley said. He also called for increased funding for AIDS vaccine research, which currently amounts to "less than 1% of all health and pharmaceutical research" (Fox, Reuters Health, 2/24). AIDS Vaccine Advocacy Coalition Executive Director Chris Collins said, "AIDS vaccine research is a long-term effort" and the North American AIDSVAX trial "has been one important step in that effort." But, he added, "[G]iven the overall finding, at this stage in the data analysis, it would be hazardous to jump to conclusions about what the AIDSVAX data mean" for African Americans and other minorities. "Such premature conclusions run the risk of raising false hopes in a world desperate for an AIDS vaccine. Further examination, and perhaps further trials, are necessary before conclusions can be drawn," Collins said (AVAC release, 2/24). "However promising this vaccine may look for black people, it is a promise for tomorrow," Phill Wilson, executive director of the Black AIDS Institute, said, adding, "AIDS is the number one killer of young black men in the U.S. because the interventions we already have don't reach enough African Americans. With or without an effective vaccine, that has to change." Wilson said, "The possibility of a vaccine that works only for African Americans should jumpstart black America's involvement in the vaccine development and approval process" (Black AIDS Institute release, 2/24).
Donald Francis, VaxGen president and co-founder, said, "We think [the findings are] scientifically and socially important. It's at least a beginning" (USA Today, 2/24). VaxGen CEO Lance Gordon said, "We intend to continue development of this vaccine through licensure, including additional studies as necessary, for use in groups in which the vaccine demonstrated a significant reduction in infection" (BBC News, 2/24). The FDA has said that it would consider approving an AIDS vaccine that was 30% effective, but the agency does not comment on products before such a decision is made, USA Today reports. VaxGen would not comment on how the agency may react to the "unprecendented" trial results, but they said it was "unlikely" that the vaccine would be approved soon, according to USA Today. "We've discussed the findings with FDA," Francis said, adding, "We will work with them to see what needs to be done to lead to licensure" (USA Today, 2/24). The FDA has already fast-tracked the review process for AIDSVAX. VaxGen later this year is expected to announce the results of another trial of the vaccine that included 2,400 injection drug users in Thailand (Kaiser Daily HIV/AIDS Report, 1/24).
A kaisernetwork.org audio HealthCast of a VaxGen telephone briefing on the AIDSVAX trial results will be available online.