THE disappointing results of the first large-scale trial of an HIV vaccine came as no surprise to vaccine researchers. 鈥淲e always knew this was going to happen,鈥� says Dennis Burton who works on HIV vaccines at the Scripps Research Institute in California.
Some news reports last week portrayed the abject failure of Aidsvax to protect most people in the trial against HIV infection as a setback for vaccine development. But most researchers gave up on this type of vaccine over a decade ago to focus on more sophisticated approaches.
Aidsvax consists of the gp120 protein that coats HIV鈥檚 surface. Several similar vaccines were developed in the late 1980s. While they did trigger antibody production, the antibodies failed to prevent infections, probably because single subunits are too different to the gp120 assemblies found on the actual virus.
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But its manufacturer, VaxGen, has plugged away with Aidsvax, carrying out a five-year trial that involved nearly 5500 high-risk people such as drug injecters and gay men in the US, Canada, Puerto Rico and the Netherlands. While the company points to positive animal tests, critics allege that VaxGen went ahead with trials for financial reasons.
VaxGen has tried to salvage something from the trial, saying Aidsvax did protect those people who identified themselves as black or Asian. For instance, it claims that the vaccine cut HIV infections in blacks by 78 per cent, and that this is statistically significant. It sounds impressive, but there were only 314 black people in the trial, and the figure is based on just four infections in the vaccine group and nine in the group given placebos instead of the real vaccine.
鈥淭hose are very, very small numbers that they鈥檙e talking about,鈥� says Burton. 鈥淚f a couple of people had gone in a different direction, it would have changed the conclusions entirely.鈥�
The company seems undaunted, saying it is discussing with the FDA whether to apply for a licence to market Aidsvax to these groups without any further trials. 鈥淚t would be irresponsible not to seek approval,鈥� says spokesman Jim Key.
Yet Aidsvax is designed only to protect against the B subtype of the virus common in the US and Europe. So even if further trials confound the experts and show Aidsvax does protect certain groups, it might not protect against the strains dominant in Africa. Another version of Aidsvax is designed to protect against the B and E strains found in South-East Asia. The results of a large trial in Thailand are due later this year.
The announcement鈥檚 timing has also come under fire. VaxGen released its results six hours earlier than scheduled, at midnight US Eastern Time on a Sunday, when most specialists who might have commented on the figures were in bed. The company says its hand was forced when The New York Times broke the story. It intends to present a more detailed analysis of the results at a conference later this month.
But most researchers are looking elsewhere, trying to create vaccines that stimulate a different branch of the immune system known as cell-based immunity. Trials of these vaccines are likely to take several more years to produce results. Improved antibody vaccines are also eagerly awaited, although these are at an even earlier stage.
Many think that defeating HIV will take a multi-component vaccine with both improved antibody-stimulating components and elements that trigger cell-based immunity (快猫短视频, 8 February, p 38). Resources should be focused on these better options, says Wayne Koff of the International AIDS Vaccine Initiative, a global organisation working to speed the development of vaccines.