Billionaire and philanthropist Bill Gates, who spends millions of dollars on AIDS drug development, said Friday he hoped for a vaccine against the disease within the next decade as a cure remains far off. “Probably the top priority is a vaccine. If we had a vaccine that can protect people, we can stop the epidemic,” the Microsoft mogul said on the sidelines of an anti-AIDS-themed concert in Paris which he backs. Since 1981, about 78 million people have been infected by HIV, which destroys immune cells and leaves the body exposed to tuberculosis, pneumonia and other opportunistic diseases. Gates said the quest for an AIDS vaccine has taken longer than expected, with many disappointments along the way. His charitable Bill and Melinda Gates Foundation spends about $400 million a year on AIDS drug research, he said, and will continue to do so for the foreseeable future. “A vaccine, that’s a big area of funding for our foundation. But even in the best case that’s five years away, and perhaps as long as 10,” he said in a question-and-answer session with young people.