An AIDS vaccine was tested on volunteers in Thailand. Half were given placebo's, and the other half the vaccine. Of the 16,000 volunteers, 74 given placebo became infected, and only 51 given the vaccine did.
The vaccine is a combination of two other, previously tested vaccines that did not have any effects on humans. Scientists say they do not know why this vaccine was more effective.
Even though the effectiveness of the vaccine is small, it is a huge step in the right direction.