Effects of Aids vaccine could be temporary

Washington: An Aids vaccine that appears to have worked at least partly in Thailand may only temporarily protect patients, with the effects starting to wane after a year or so, researchers reported on Thursday.

That may explain why results of the experimental vaccine have been so difficult to interpret, said Dr. Nelson Michael, a colonel at the Walter Reed Army Research Institute of Research in Maryland, who helped lead the trial.

Michael's team is trying to find out how or why it might have worked. They surprised the world last September when they showed the experimental vaccine cut the risk of infection by 31 per cent over three years.

"It is very likely that this vaccine only worked for a short period of time," Michael said in a telephone interview. "It is a weak, a modest effect but something that we can build on."

The vaccine is a combination of Sanofi-Pasteur's Alvac canarypox/HIV vaccine and the HIV vaccine Aidsvax made by a San Francisco company called VaxGen and now owned by the non-profit Global Solutions for Infectious Diseases.

Trial redesign

Michael told the Conference on Retroviruses and Opportunistic Infections in San Francisco that it may be possible to design a trial that will show better whether the vaccine can really help people.

Part of the problem, he said, was that the 16,000 Thai volunteers who tested the vaccine were not at especially high risk of Aids infection.

He said he would work with Dr Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases, to design trials in Asia or Africa.

According to the United Nations, more than 33 million people are infected with the Aids virus, with 2.7 million new infections every year. Even a vaccine that protected for just a year would be useful.