HIV vaccine trial 'landmark moment'

Early results from the first experimental vaccine to prevent HIV infections have been validated, researchers reported on Tuesday at an international conference.

"We believe this is the first milestone that will lead us ultimately to be able to develop a globally effective vaccine for HIV," said study author Dr. Nelson Michael, a colonel at the Walter Reed Army Institute of Research in Rockville, Md.

"We've likened this to a baby's first steps. But we need to generate a daughter who can be a marathon runner and she's not there yet."

Michael and his Thai research partners stressed it will be years before a vaccine is widely available. But their results prove that a vaccine will one day be possible — the first results to show a modest ability to protect people from HIV infection.

Vaccine combo

Last month, the team announced that a two-vaccine combination cut the risk of becoming infected with HIV by 31 per cent in a trial of more than 16,000 volunteers in Thailand.

The full results were published online Tuesday in the New England Journal of Medicine, and presented at a scientific conference in Paris. The latest research includes more analysis suggesting the vaccine is beneficial.

There is no definitive proof, since only 125 study participants became infected, said Dr. Anthony Fauci, director the National Institute of Allergy and Infectious Diseases, the study's main sponsor.

The vaccine combination was tested in HIV-negative Thai men and women ages 18 to 30 at average risk of becoming infected.

Half received four doses of Sanofi-Pasteur's ALVAC canary pox/HIV vaccine and the failed HIV vaccine AIDSVAX, made by a San Francisco company called VaxGen, and now owned by the nonprofit Global Solutions for Infectious Diseases.

'Phenomenal moment'

The vaccine combo reduced the risk of infection by 31.2 per cent over three years, according to one analysis of the data, which excluded seven subjects who were later found to be infected with HIV before they were vaccinated. 

The researchers also did two other types of analysis of the data. One approach, called intention-to-treat, showed vaccine effectiveness of 26.4 per cent. The other, called a pro-protocol analysis, showed the vaccine combination was 26.2 per cent effective.

"This is a phenomenal moment, a landmark moment for all of us," said Canadian physician Alan Bernstein, who heads the Global HIV Vaccine Enterprise, which includes governments, HIV scientists, the World Health Organization and funders such as the Bill & Melinda Gates Foundation.

Now, four working groups as well as the wider research community will begin the next phase of work toward a vaccine, to understand how the combination worked and to see whether it can be improved, said Dr. Catherine Hankins, a Canadian who is chief scientific adviser to UNAIDS in Geneva. 

"What would we need to do to enhance the effects we saw," Hankins said.

Unanswered questions

The vaccine appeared nearly twice as effective among those at low or moderate risk of becoming infected, compared with people at high risk because they share needles, have contact with prostitutes or engage in other risky behaviours, though the finding was not statistically significant.

"Perhaps the requirements for protection against transmission in low-risk heterosexual persons are considerably different or less stringent," Dr. Raphael Dolin, of Beth Israel Deaconess Medical Center in Boston, wrote in an editorial published by the medical journal.

Other questions that still need to be answered include how long the vaccine's effects last and the relative contribution of each of the vaccine's components, the editorial said.

The trial was sponsored by the U.S. government and the Thai Ministry of Public Health.