Antiretroviral drugs are used to combat HIV
Scientists are testing a vaccine designed to give HIV patients a prolonged break from their regular medication without side effects.
The Aids 2008 conference in Mexico City was told 345 patients in 21 centres in the US and Europe will take part in the largest-ever trial of its kind.
The vaccine has been developed by a biotechnology company based in Norway, Bionor Immuno.
Results from the trial are due by the end of 2009.
A break from standard HIV therapy would potentially alleviate the adverse side effects associated with the drugs, which can include problems with the heart and liver, diarrhoea, nausea and fat loss
It may also help delay the emergence of drug-resistant viruses, as well as providing substantial savings for health care services.
Dr Barry Peters, of Kings College London, is leading the research in the UK.
He said: "A successful immunotherapeutic HIV vaccine would give patients and doctors enormous advantages over current treatments, both in developed and developing countries.
"Even if this vaccine is not the final answer, it could help the march towards a successful immunotherapeutic HIV vaccine."
However, he stressed the vaccine was still at a very early stage of development.
The vaccine works by stimulating an immune system response, in contrast to standard HIV drugs, which block replication of the virus.
It has already been tested in two small trials on 11 and 38 HIV patients with promising results.
The majority of patients were able to refrain from taking their usual antiretroviral therapy (ART) for an average period of 31 months.
During this time their level of key infection-fighting CD4+ cells remained high above the level they had before they started taking ART.
At a follow up 44 months after treatment interruption, 34% of the patients were still not back on ART.
Some patients were still off ART five years after the trial was completed.
ART usually cannot be interrupted for more than three to four months without side effects.
Lisa Power, head of policy at Terrence Higgins Trust said: "Any advance that gives people more treatment choices and delays the progress of the virus is a good thing.
"We are not yet clear whether this vaccine will work, but we'll know more by the end of next year."