Aids vaccine progress

Fresh results from the world's first successful test of an experimental Aids vaccine confirm that it is only marginally effective and suggest that its protection against HIV infection may wane over time.

Yet the findings are exciting to scientists, who think that blood samples from the trial may show how to make a vaccine that does a better job.

The results also hint that the vaccine may work better in the general population than in those at higher risk of infection, such as gay men and intravenous drug users.

It is the first time an Aids vaccine has been tested mostly in heterosexuals at average risk, and doctors have long known that how a person is exposed to HIV affects the odds of becoming infected.

Last month, researchers announced that a two-vaccine combination cut the risk of becoming infected with HIV by more than 31 per cent.