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Researchers Rebound From Latest AIDS Vaccine Failure


 

MEXICO CITY — The development of an AIDS vaccine is likely to take a long time, and research needs to be more selectively focused on the most promising candidate vaccines, given the recent failure of the latest leading candidate to prevent infection in a large international trial, according to the findings of a report aimed at setting priorities for AIDS vaccine research.

Experts at the International AIDS Conference discussed the status of AIDS vaccine efforts at a press conference to unveil the AIDS Vaccine Blueprint 2008. The document, published by the International AIDS Vaccine Initiative (IAVI), is the fifth biennial report of its kind. It comes at a time when optimism in the field is waning, after early closure of the STEP trial of the failed vaccine last year and cancellation of the PAVE 100 trial of a new vaccine this year.

The blueprint delineates the current challenges in developing an AIDS vaccine, and provides interim milestones for each. “This is a way to measure [progress], to hold people accountable,” explained Dr. Seth Berkley, president and CEO of IAVI.

The blueprint calls for pruning the vaccine pipeline. “We believe that the majority of the 30-odd candidates that are in the pipeline should be prioritized based on their probability of success,” he said. This recommendation is not new, he acknowledged, but the document goes further, detailing how it should be done by requiring vaccine candidates to be superior to ones that have failed in preclinical testing.

In recent years, more stakeholders have rallied behind the blueprint, which will be critical going forward, according to Dr. Peter Piot, executive director of UNAIDS in Geneva. “This [AIDS vaccine development] is not going to be something that can be done by one organization. It requires a coalition,” he said.

“Science is never a straight line. Failure is part of the game,” noted Dr. Alan Bernstein, executive director of the Global HIV Vaccine Enterprise in New York. As disappointing as the STEP trial's results were, the trial has been a success in the sense that it provided, and continues to provide, a wealth of data that will help inform future trials.

Given the retroviral nature of HIV and the lack of much precedence in developing vaccines against retroviruses, he applauded recent efforts by several organizations to stimulate diverse approaches to the problem.

Putting the AIDS vaccine effort into context, Dr. Berkley noted that the development of a vaccine typically takes decades. Advancing HIV vaccine research will require not only new talent, but also stable, predictable, and flexible financing, he continued. Flexibility is important because “we need to be able to jump on advances and quickly drop things that aren't promising.” This ability to be flexible will be critical to maintaining incentives that keep companies engaged in the effort.

In response to calls to end the vaccine research effort, Dr. Piot cited the disease's staggering toll. “If the world can be satisfied with 2.7 million people infected per year—7,500 per day—then I am not so sure where the standards are for declaring something a total disaster,” he said.

Shutting down the AIDS vaccine trial sites in Africa would be “a big mistake,” agreed Dr. Omu Anzala, chairman of microbiology at the University of Nairobi (Kenya) and director of the Kenya AIDS Vaccine Initiative (KAVI). He noted that these sites not only stand ready for future trials, but also continue to conduct epidemiological and basic HIV research. “It is this information that will then feed into HIV vaccine discovery and also feed into drug discovery,” he said.

Dr. Anzala agreed with his colleagues that the failure of a single vaccine is not cause for condemning the entire AIDS vaccine initiative. Noting that he comes from a country known for long-distance running, he likened the search for an effective vaccine to a marathon in which perhaps 100 runners start and many fall by the wayside, but eventually one wins. “We cannot stop now,” he concluded.

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