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"I think we need to look at the bright side and hope that this is an advance," said Dr. Yang.
Researchers gave 8,000 volunteers an AIDS vaccine, made of two vaccines that didn't work before. Another 8,000 people got a placebo. After three years, the vaccine group ended up with 51 people who got HIV infected compared to 74 people in the control group.
"It has some, although albeit modest, results, some very encouraging results that can be used to guide further efforts in vaccine development," said Maureen Birmingham from the World Health Organization.
It's the first time any vaccine has appeared to show any difference.
While many remain optimistic, experts urge caution in how the results are interpreted. The number of people infected was so small it's difficult to tell if the results were due to the vaccine or to random chance.
"Could you see this pattern happen without it being due to the vaccine? That's the important question that we really need to think about," said Dr. Yang.
If these vaccine results can be duplicated, it's only the beginning of a long, arduous process. But creating an AIDS vaccine is very problematic. HIV has mutated into many, vastly different strains. So Dr. Yang says scientists are trying to do something they've never done before.
"We're talking about inventing something. And if you haven't invented it yet, it's hard to know if it's possible," explains Dr. Yang.
Dr. Yang says it's difficult to produce an AIDS vaccine because current vaccine's bolster the immune system's natural response where as the natural response to HIV is immune system failure.
This new AIDS vaccine is reported to have 31 percent efficacy compared to a reported 70 percent efficacy for the swine flu vaccine.