An AIDS vaccine unveiled on Thursday that cuts the risk of HIV infection by a third is "good news but the effect remains modest", one of France's top AIDS scientists said.
"This is the first time an HIV vaccine has been shown to have a significant effect in clinical trials in preventing infection," said Jean-Francois Delfraissy, director of France's National AIDS Research Agency.
"After many long and difficult years, it provides encouragement for continuing the effort" to develop an AIDS vaccine, he said.
The rapid identification of the AIDS virus after the disease emerged in the early 1980s fueled optimism that a vaccine would quickly emerge, but none of the dozens of candidate drugs tested since then have worked until now.
The new vaccine, a combination of two drugs that failed to impede infection on their own, was tested in Thailand in clinical trials on more than 16,000 adults.
But Delfraissy cautioned that, while encouraging, the new vaccine's "impact remains modest". "We don't yet have a vaccine against HIV," he said.
A 31 per cent reduction in the risk of infection "is insufficient by a wide margin. This is not a vaccine tool that can be used by public health services for the population at large," he said.
Earlier studies have shown that circumcision reduces the risk of infection among men by 55 to 60 per cent, he pointed out.
AIDS first came to public notice in 1981 and has since killed at least 25 million people worldwide, and 33 million others are living with AIDS or the HIV virus.