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The lesson from 2 failed trials: The science must be more vigorous, experts say

MONDAY, Dec. 1 (HealthDay News) -- Nobody said HIV would give up without a fight.

As World AIDS Day arrives Dec. 1, scientists are taking a sobering look back at what went wrong in recent, high-profile failures of two human trials of candidate AIDS vaccines.

The consensus: A viable vaccine is still very possible, and with it comes the potential to wipe out HIV/AIDS. But the science behind any new candidate vaccine must be much stronger than it has been in the past before testing begins in humans.

"We are going to be better served to try and find out the basics of what the immune response is to HIV, what the limitations are, and how we can tweak or change that, or come up with something entirely new," said Rowena Johnston, vice president of research at the Foundation for AIDS Research (amFAR) in New York City. "And only then can we start to think about a product that could be taken into humans."

Just two potential HIV vaccines have made it so far to human clinical trials: VaxGen's AIDSVAX, tested in Thailand, until the trial was stopped in 2003; and Merck & Co.'s HIV vaccine, which was tested in North and South America, the Caribbean and Australia, until it proved a failure in 2007.

In the Merck case, the trial results have also been shadowed by speculations that the vaccine somehow tweaked some recipients' immune systems to make them slightly more vulnerable to HIV infection.

Some experts in the field now believe that both vaccines were rushed too soon into human trials. One big flaw: Primate trials matched the vaccine to the strain of HIV the monkey was exposed to. That's unlike "real world" human infections, where people may be randomly confronted with any number of strains, experts said.

"What you want to do is have evidence in primates that you can block completely, or ne
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