New York, NY, 15 January 2004 - The Treatment Action Group (TAG) expressed concern today regarding the weak scientific rationale for proceeding with the first National Institutes of Health (NIH)-sponsored AIDS vaccine efficacy trial. The trial is currently recruiting 16,000 Thai volunteers at a low risk of HIV infection in order to assess the protective efficacy of a vaccine regimen that combines a canarypox viral vector (ALVAC cp1521, manufactured by Aventis Pasteur) with a protein "boost" (AIDSVAX, manufactured by VaxGen).

TAG echoes the sentiments expressed in an opinion piece signed by many leading AIDS researchers and published today in Science Magazine entitled "A Sound Rationale Needed for Phase III HIV-1 Vaccine Trials" [Burton, DR et al. A Sound Rationale Needed for Phase III HIV-1 Vaccine Trials. Science, 303;5656.] The researchers point out that the immune responses induced by the ALVAC vaccine are weak and typically only detected in less than one third of immunized individuals. It is this shortcoming of ALVAC that led to the cancellation of a planned US-based phase III efficacy trial two years ago. Furthermore, the AIDSVAX vaccine that is being employed as a "booster" in the current trial has now failed to show efficacy in preventing HIV infection in two separate corporate-sponsored phase III studies — one of them international and one carried out in Thailand. The data thus offer little hope that this vaccine combination will be able to offer any protection against HIV, calling into question the rationale for the current efficacy trial. As the authors of the Science Magazine opinion piece note, there are now many newer vaccine candidates progressing through phase I and II trials that can reliably induce the strong cell-mediated immune responses that ALVAC largely fails to elicit. It is highly likely that some of these candidates will be ready for efficacy trials before the current ALVAC/AIDSVAX trial is even completed.

TAG believes that it would be a far better policy to prioritize the development and testing of these newer and more potent vaccines rather than waste human and financial resources — estimates range up to $120 million for the cost of this study — on a trial that is extremely unlikely to lead to an effective and licensable AIDS vaccine. Even if the current trial proceeded to conclusion and did show some degree of vaccine efficacy, the design of the study would make it impossible to know whether ALVAC alone was responsible, or if the addition of AIDSVAX had improved — or worsened — the outcome. A second, even larger phase III efficacy trial would then have to be performed in order to answer this question — a mind-boggling example of short-sighted planning for which the NIH should be called to task.