AIDS vaccine effects may wear off

Shot appears to lose its strength after about a year, researchers say

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 percent 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 nonprofit Global Solutions for Infectious Diseases.