There's good news about AIDS vaccine research. The World Health Organization and UNAIDS say the largest ever HIV vaccine trial has yielded "very encouraging" results. The agencies say, "It's the "first demonstration that a vaccine can prevent HIV infection in the general population."
The announcement was made Thursday in Thailand, where the clinical trial, involving over 16,000 adults, was conducted.
Mitchell Warren, head of AVAC, the AIDS Vaccine Advocacy Coalition in New York, calls the results a "historic milestone."
"For 25 years now the world has looked for an AIDS vaccine and we have had clues that an AIDS vaccine was possible…. But it's only with the trial results announced today that we now have our very first evidence in human trials that an AIDS vaccine is possible to actually reduce the risk of HIV infection," he says.
Good news follows bad
Two years ago, what was thought to be a promising vaccine candidate from Merck failed to protect against infection in clinical trials. The findings were a considered a major blow to HIV vaccine research and many questioned research models. So what happened?
"Science happened. And that is what I think this result today tells us more than anything. Science happens in a remarkable, unpredictable way," he says.
Warren says the Merck trial was not a total failure.
"The trial succeeded in answering a question. Unfortunately, the answer was that that particular candidate…didn't work.
He adds, "What's amazing is that the trial result announced today has been in the clinical trials for six years now. And it was ongoing throughout that entire life of the Merck vaccine trial. And people pretty much dismissed this vaccine from working."
Encouraging, yes, but…
Warren says the Thailand trial involved a two-vaccine combination had "a modest effect." So it's not ready to roll out for general use.
Modest, he says, in that the "group that got vaccine had about a 30 percent reduced chance of getting infected than those people who got the placebo – so about 30 percent fewer infections in the vaccine group."
He calls the results a building block on which to build a better vaccine.
So how high an efficacy rate is needed before a vaccine is ready to be rolled out?
"The process of determining how good is good enough is much more than a single number from this trial. It really gets decided by regulatory authorities in various countries, by communities in those countries. And there isn't a straight answer to what is the magic number to say this is good enough to roll out," he says.
Other factors come into play
Besides a higher efficacy rate, researchers still need to know how often a person may need to get the vaccine, whether it could be manufactured on a large scale and at what cost.
"Would this same vaccine work in another part of the world where the HIV strain is different? We don't know…. This is not the beginning of the end of the epidemic, this is the end of the beginning, a new chapter, really, in our search," he says.
The International AIDS Vaccine Initiative (IAVI) joins AVAC in praising the vaccine trial results. IAVI President Seth Berkley (MD) says, "The outcome is very exciting news and a significant scientific achievement…. Now we've got a vaccine candidate that appears to show a protective effect in humans, albeit partially."
Berkley says the Thailand trial proves the importance of human trials.
"We can only learn so much from animal models. We could not have learned what this study is going to teach us any way other than through clinical research, and we expect to learn a great deal," he says.
But IAVI, AVAC, WHO and UNAIDS say despite the promising results, access to care and treatment of HIV/AIDS remain top priorities.