A trial HIV vaccine that cuts infection rates by almost a third has provided the research community with some hope following years of setbacks.
The vaccine, a combination of two earlier experimental vaccines that had not reduced infection rates individually, is the first to prevent infection. It was given to 16,000 Thai volunteers in the world's largest HIV/AIDS vaccine trial, carried out by the Thai government and the United States army.
The male and female volunteers, all HIV negative and aged between 18 and 30, were split into two groups — half were given a placebo, and half given the vaccine. All were provided with condoms and counselling on HIV/AIDS prevention.
Over the course of the trial, 74 people from the placebo group and 51 in the vaccine group became infected. Scientists say the results are statistically significant — with a 31.2 per cent lower risk of infection for the vaccinated group.
"This result is tantalisingly encouraging," says Richard Horton, editor of The Lancet. "The numbers are small and the difference may have been due to chance, but this finding is the first positive news in the AIDS vaccine field for a decade."
The vaccine is based on the B and E strains of HIV most common in Thailand, and it is not known whether the vaccine will be effective against other strains elsewhere in the world, such as the C strain predominant in Africa.
Nevertheless, the international community have shown their support. The WHO say that though the results are "modestly protective", they have "instilled new hope in the HIV vaccine research field".
Even a partially effective vaccine could have a big impact. Two million people died of AIDS in 2007, and every day, 7,000 people worldwide are infected with HIV, UNAIDS estimates.
Alan Bernstein, director of the Global HIV Vaccine Enterprise is hopeful that with more research, "it will be possible to develop a vaccine that is fully protective against HIV".