International AIDS vaccine advocates said recent studies showing first evidence of vaccine-induced protection in humans and evidence that drugs designed to treat AIDS can also be used for prevention were signs of a "renaissance" in the search.

"This is a pivotal moment in HIV vaccine research," said Alan Bernstein, executive director of the Global HIV Vaccine Enterprise. "The last five years have been the richest period in HIV vaccine research since the epidemic began. The question... now is how do we build on these scientific advances?"

Bernstein, whose group published a report on the "road to prevention" ahead of a major international conference on AIDS starting in Vienna on Sunday, said cross-border and cross-discipline collaboration among scientists was crucial.

And at a time when a global economic recession is squeezing funding for the AIDS battle, trying to attract new minds and ideas would be as important as trying to bring in new money.

There are around 20 drugs on the market to treat HIV and prevention measures have been deployed to try to stop its spread, but no vaccine exists against the human immunodeficiency virus (HIV) that causes AIDS. Since the AIDS pandemic started in the early 1980s, almost 60 million people have been infected with HIV, many of them in Africa, and it has killed 25 million.

In September 2009, scientists reported their biggest success yet with an experimental vaccine that showed a modest effect and appeared to slow the rate of infection by about 30 percent in Thai volunteers. And earlier this month, U.S. researchers found antibodies that can protect against a wide range of AIDS viruses and said they may be able to use them to design a vaccine.

OPTIMISM

Microsoft founder and philanthropist Bill Gates, whose Gates Foundation spends a large portion of its $34 billion fund on fighting AIDS, says he is now "optimistic about an HIV vaccine" -- despite having said in 2005 "I'll eat my hat" if one were developed in the next decade.

"The scientific results we've seen with the antibodies...and the Thai trial...really point us toward what we need to do," he told reporters at a briefing ahead of the Vienna conference.

Bernstein pointed to several ways to strengthen HIV vaccine research and development, including getting more clinical trials up and running to test new ideas in humans, and expanding trials to those countries where people are most at risk of HIV.

There is also a need to speed up data sharing from trials and focus resources on the most promising scientific areas.

"Despite their fundamental importance to HIV vaccine development, only three vaccine concepts and four clinical efficacy trials in humans have been completed in 27 years since the virus was first identified," the Enterprise report said. "With little clinical efficacy data to draw upon, many questions critical to guiding new approaches...remain unanswered."

Seth Berkley, director of International AIDS Vaccine Initiative (IAVI), said the recent advances showed that research funding over the past decade was paying off. But he warned that the global financial crisis had already led to a 10 percent fall in investment in HIV vaccine research and development.

"This is not the time to slow the effort," he wrote in a commentary in the New England Journal of Medicine. He said creating an effective vaccine would need innovation from academia and the drug industry, long-term, stable funding and "contributions from the best and brightest young scientists."