Against the Odds, Company Works on AIDS Vaccine

VaxGen's AIDSVAX vaccine is based on some of the earliest knowledge of HIV and is the only HIV vaccine currently in Phase III clinical trials -- the last step before a vaccine or drug maker can seek approval from the Food and Drug Administration.

About 30 other vaccines are in earlier stages of human testing. Unlike those using a live but weakened or "killed" virus, AIDSVAX uses two proteins based on the gp-120 protein found on the outside envelope of the virus. The hope is the body's immune system can become sensitized to anything carrying gp-120 and will mount a response to the virus. Results from the trial, which started in June 1998, will be revealed early next year.

VaxGen has immunized two-thirds of the 5,400 volunteers in its first Phase III trial -- 5,000 homosexual or bisexual men and 400 women considered to be at high risk of getting HIV. No one knows who got the real vaccine and who got the placebo shot; this information will be "unblinded" early next year. Researchers hope fewer vaccinated subjects than unvaccinated subjects will develop HIV. Dr. Ronald Francis, founder and president of VaxGen, said trials in chimpanzees showed it worked well. "I'm confident from the chimpanzees that the vaccine will be efficacious. The question is, how efficacious," he said. "Everybody who gets the vaccine has a good antibody response," Francis said. He hopes measurements of antibody levels will work as a correlate to show whether the vaccine is working.

Even if just 20 percent of those vaccinated are immune to HIV infection, Francis believes this could have an impact on the AIDS epidemic. Vaccinated volunteers who do become infected will be followed for two years to see if the vaccine at least makes HIV grow more slowly in the body.

HIV subtype B is found mostly in Europe, the Americas and Japan, while subtypes A, C, D and E are spreading in Africa and Asia. The first version of AIDSVAX, tested in the United States, Canada and the Netherlands, targets the B subtype. A B/E subtype vaccine is being tested in Thailand in trials that will finish at the end of next year.

Back to other CDC news for November 22, 2002

Previous Updates