Many have tried and failed to create a vaccine that could prevent infection with HIV. Now, Canadian researchers say they're working on one that takes a different approach.

Researchers from the University of Western Ontario in London, Ont. say they have developed an HIV vaccine that uses the whole HIV virus, unlike other attempts that have used just certain genes or proteins from the virus.

The virus has been genetically engineered to be "non-pathogenic," meaning it can't actually cause HIV in recipients. The idea is the vaccine would prime the body's T-cells to destroy any cells that might become infected with HIV.

So far, the vaccine has been shown to stimulate a strong immune response in preliminary toxicology tests in lab animals, the university reports. But it will be several years before researchers know whether it's effective in humans.

The team announced Tuesday they have just received approval from regulators with the U.S. Food and Drug Administration to begin testing the experimental vaccine on humans. The Phase I clinical trial will begin in January using 40 volunteers who already have HIV. That phase will test the safety of the vaccine.

If all goes well, the next phases of study would test whether the vaccine is actually effective.

Phase II would measure immune responses to the vaccine in people who are HIV negative. Phase III would test the effectiveness of the vaccine in a larger group of about 6,000 volunteers who are at risk of becoming infected. Half would be given the vaccine and half given a placebo. Participants would then be tracked for three years to see how many in each group become infected.

The vaccine, dubbed SAV001, was developed by Dr. Chil-Yong Kang and his team over the last 10 years, and is the only HIV vaccine currently under development in Canada.

The vaccine was developed with support from Sumagen Canada, a biotech company established in 2008 specifically to support clinical development of Kang's vaccine. Sumagen Canada is a subsidiary of Sumagen Co. Ltd., a Korean-based pharmaceutical venture company.

A number of pharmaceutical companies and academic researchers around the world have tried to develop a vaccine against HIV, but all have ended in failure.

One large study in Thailand showed an experimental vaccine offered some protection against infection, but only in about a third of recipients. Researchers continue to work on that vaccine to improve it.

Earlier this year, researchers halted a study that was testing a daily HIV prevention pill called Truvada in thousands of African women, after partial results showed the pill was ineffective.

The World Health Organization estimates that 34 million people are living with HIV around the world, and that 2.7 million people are newly infected every year.