South Africa's new health minister called on Monday for renewed global efforts to find an Aids vaccine, signalling a sharp change from her controversial predecessor in a country with the world's most HIV/Aids infections.

"It was imperative to get ahead of the curve of this epidemic 10 years ago. We all for various reasons have lost ground," Barbara Hogan said at the opening of an international meeting of scientists searching for ways to prevent Aids.

"It's even more imperative now that we make HIV prevention work. We desperately need an effective HIV vaccine."

Her remarks were in marked contrast to those of her predecessor, Manto Tshabalala-Msimang, who was derided as "Dr Beetroot" for championing use of the vegetable to fight HIV/Aids.

Hogan took over the ministry in a political shake-up last month, in a move hailed by activists as an end to Tshabalala-Msimang's policies that for years questioned whether the HIV virus causes Aids.

Hogan slams wasted time

"We know that HIV causes Aids. The science of HIV and Aids is one of the most researched subjects in the medical field," said Hogan, later slamming "wasted time" which contributed to the country's high Aids prevalence.

Some 5.5 million people out of South Africa's 48 million population are living with HIV/Aids.

Researchers at the conference welcomed Hogan with open arms, welcoming the end of denialism about HIV/Aids in South Africa.

Vice chancellor of the University of KwaZulu-Natal, Malegapuru Makgoba said it was a relief to finally reach a point where everyone agreed HIV causes Aids.

"It is a liberating experience, you don't know how long we have suffered in bondage about this issue."

Some 900 researchers and scientists are attending the conference, being held for the first time outside of the United States or Europe.

A great need for a vaccine

"This is a country with the greatest number of HIV infections in the world. Nowhere else is the need for a vaccine greater than right here," said conference chair Lynn Morris.

"As we all know the field is at a turning point. One thing is clear, we need to continue with these steps and they need to be bold. The field needs more input, fresh ideas and new directions."

A quarter of a century after HIV/Aids first became widely known, the search for a vaccine has proved unsuccessful and the pandemic continues unheeded, with about 33.2 million people living with HIV worldwide in 2007.

The drive for a vaccine has suffered several setbacks as two recent clinical trials proved test drugs were ineffective or appeared to heighten chances of becoming infected.

The two trials, conducted in the United States and South Africa, were the most promising candidates for a vaccine, and their failure stunned scientists who have questioned the safety of putting people into the test groups.

Researcher Stanley Plotnick, who has worked on several vaccines, said a trial under way in Thailand could provide a step forward.

"If that vaccine even shows potential success, it will turn things around completely," he said.