It will take six to eight weeks before results show whether experimental swine flu vaccines are effective. (Canadian Press)

The world's first human trials of a swine flu vaccine have begun in Australia, drug company officials said Wednesday, with the aim of controlling the virus that has so far killed more than 700 worldwide.

Two biotechnology companies have started injecting adult volunteers in the southern city of Adelaide with their vaccines.

Adelaide-based Vaxine began trials Monday with 300 subjects, and Melbourne's CSL has 240 people in its seven-month trial, which started Wednesday. The companies say their trials are the first tests of a swine flu vaccine on humans.

At least 41 people have died in swine flu-related illness in Australia, which is well into its winter flu season.

"We're in the Southern Hemisphere, and that is where the problem is right now," Vaxine research director Nikolai Petrovsky told The Associated Press.

"The demand was here yesterday. We're right in the middle of a surge of swine flu cases where perhaps the United States won't have to worry about it as much until their flu season hits in six months."

Australia had confirmed 14,703 cases of swine flu as of Wednesday. The worldwide death toll from swine flu is more than 700, according to the World Health Organization, which recently stopped counting the number of cases worldwide.

No guarantee vaccine will work

An explosion of cases is predicted in September and October, when students and workers in the Northern Hemisphere return from summer vacation.

CSL expects that initial results will allow distribution of its government-funded vaccine in October. The federal government has already ordered 21 million doses of CSL's vaccine for use in Australia, should it be proven to work.

"We have a specific vaccine that we believe will be able to protect millions of people against this new H1N1 flu," Andrew Cuthbertson, CSL's director of research and development, told reporters. He called swine flu "a novel strain of influenza" and said the trial would determine the dose and schedule of the vaccination.

Vaxine's Petrovsky said it would be six to eight weeks before results would verify whether a vaccine was effective.

"There is no guarantee any of these vaccines will work," he said. "Swine flu is a very peculiar beast, it's a very different virus that we're dealing with. But we are hopeful."

Medical experts warned against rushing the vaccines through trials.

"I think it's important for the public to know that they're going to get a safe and effective vaccine," Andrew Pesce, president of the Australian Medical Association, told Sky News television.

"No one will give anybody brownie points for putting out a vaccine that didn't work or caused harm."