nationwide swine flu vaccination

Australia's chief medical officer is expecting to begin a nationwide swine flu vaccination program in October.

The Federal Government has ordered 21 million doses of a swine flu vaccine, which is still being tested.

Professor Jim Bishop told the Seven Network the vaccine order would cover all of the nation's population if only one dose is needed, or half the population if two doses are required.

He said the launch of the immunisation program will be dependent on successful trials of the vaccine.

"We need to do some trials to make sure it's safe, so we're saying by October we should be able to start a program, but that depends really on manufacture being successful," he said.

The World Health Organisation (WHO) now says the pandemic is "unstoppable".

There have been more than 9,000 cases of swine flu in Australia including 19 deaths.

Professor Bishop says he wants to make the vaccine as widely available as possible because the virus can be severe in some cases.

"Most people will go through it and have a very mild illness which they recover from very quickly," he said.

"But we are seeing a few people now thrown up that have other medical conditions, being unwell and also we are seeing a few people that were previously well but are severely affected by the disease."

Professor Bishop says he expects the virus to linger on after the flu season is over.

"We're more concerned about the second wave of this thing, which might be more severe than the first," he said.