The VaxGen Study
A Phase III Vaccine StudyOn Monday, February 24, the initial results were announced from VaxGen's AIDSVAX vaccine trial, the first Phase III HIV vaccine trial. Initial results indicate that the AIDSVAX vaccine was not effective in preventing HIV in the overall group of vaccinated volunteers.
Though it is disappointing that AIDSVAX did not demonstrate efficacy in the study, the completion of this trial should be considered a success. Trial participants helped show that a Phase III HIV vaccine trial is possible, an important step in HIV vaccine research. This trial and the important information being gathered from it would not have been possible without the time and dedication of the study volunteers. Chris Collins, Executive Director of The AIDS Vaccine Advocacy Coalition (AVAC) said, "This trial should not be characterized as a failed effort. More human trials of better candidates in several countries will likely be necessary to identify an AIDS vaccine. ... AIDS vaccine research is a long term effort. The North American AIDSVAX trial has been one important step in that effort."
This historic trial was conducted in the continental US, as well as Puerto Rico, Canada and the Netherlands. The trial enrolled 5,095 men who have sex with men (MSM) and 308 women, all HIV-negative. The Seattle HIV Prevention Trials Unit (HPTU), a University of Washington program, enrolled 135 MSM and at the end of the three-year trial had a 94% retention rate!
The primary results were based on data of 5009 volunteers who completed at least three of the seven scheduled injections, two thirds of whom received AIDSVAX and one third who received a placebo. Among all the volunteers 5.7% (191) of the group who received AIDSVAX became infected and 5.8% (98) of those who received the placebo became infected. (See table below.) These results indicate that, unfortunately, the AIDSVAX vaccine did not prevent HIV infection.
In reporting the results the company went on to say that there was a trend towards higher levels of efficacy among non-Hispanic ethnic groups, specifically African-Americans. VaxGen said that the subset analysis showed that among the 314 African American participants in the study, 8.1% of those receiving placebo (9/111) became infected with HIV compared with 2.0% receiving AIDSVAX (4/203), a vaccine efficacy of 78.3%. Many questioned the credibility of these results since it is not statistically reliable to do a post-hoc subgroup analysis to look for trends as eventually you will find one. This report has brought much controversy and criticism to the company. It led to conflicting news headlines. More analysis is necessary before being able to draw any conclusions about the vaccine's effects in any subpopulation.
There were many lessons learned from this first ever efficacy vaccine trial. We now know that large-scale trials can be done. Trial participation did not seem to affect behavior (higher risk taking). We know that we need to make sure to have greater diversity in all trials and that an efficacy trial MUST reflect the epidemic. HIV vaccines need to be developed in the context of a larger prevention effort. HIV vaccine research is a marathon, not a sprint. Initial vaccines may be partially effective. Community education is critical not only in trials, but we must continue to promote safer sex and safer injection behaviors. Anti-retroviral therapy (ART) is complementary and not competitive with HIV vaccine development.
An HIV vaccine represents our best hope to end this pandemic.
There is Hope.
Dr. Lara Strick is a member of STEP's Board of Directors, and is completing her Fellowship in Infectious Diseases at the University of Washington.
This article was provided by Seattle Treatment Education Project. It is a part of the publication STEP Perspective.
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