A TERRORIST on a suicide mission could just as likely be armed with smallpox as a bomb and the impact on Australia from such an attack might only be as far away as an overseas tour group, US experts say.

Director of the US National Institute of Infectious Allergy and Diseases, Dr Anthony Fauci, says Australia will soon have to make a difficult decision on how to deal with the threat of smallpox.

In the US the Government planned to vaccinate a core of military and health workers as "first responders" against smallpox and Dr Fauci says Australia may have to take similar action.

It's a decision that has to be made knowing the risks for smallpox vaccination are one-to-two deaths (and from 15 to 49 life-threatening complications) per million people vaccinated.

"Australia has to make their own decision," Dr Fauci, among US President George W Bush's smallpox policy advisers, said.

"They have to make that decision based upon their assessment of what the threat to them is.

"Either from a direct attack on Australia or from an attack for example in the Middle East and then people travel back and forth to Australia."

And the Bali bomb attacks that killed 88 Australians were evidence the country was not immune from chemical attack either.

"Australia at least in its citizenship has been the victim of a terrorist attack," Dr Fauci said.

"We ourselves are twice victims, once on September 11 and once with the anthrax attack."

"In the United States we had to make a very difficult decision because we know that the risk is not zero of smallpox.

"But we can't quantitate it, we can't say there's a 10 per cent chance, or a 20 per cent chance or a 30 per cent chance that there'll be a bioterrorist attack either on the US, or in place that ultimately might spread to the US.

"We made it very clear, the President made it very clear, the Secretary of Health and Human Services and I made it very clear, that we do not recommend routine vaccination for the general population.

"Not many countries are seriously considering vaccinating their entire population."

Dr Fauci said his advice was that ordinary people should not get vaccinated against smallpox.

But he said a group of healthcare workers, smallpox response teams and first responders like firefighters and policemen should be vaccinated in case of an attack so those people could mobilise themselves quickly.

"If nobody's vaccinated and then there's a massive attack the people who are going to go in and try and put the fire out are going to be susceptible themselves," he said.

The vaccine in use is still the same as that used last century and is tarnished with potential side effects despite ongoing attempts by government and private companies to develop or import something safer.

Professor of preventive medicine at the University of Southern California Dr Thomas Mack, a veteran of the 1960s smallpox wars in South Asia, has argued that today's media-drenched society would give a community ample warning of an outbreak and good opportunity to contain its secondary spread.

"I would be against getting a vaccination policy of healthy Australians," he said.

"And I would also be against vaccinating hospital populations - the staff that is - in the way that the Bush Administration is doing it for the same reasons.

"In Australia I would imagine that ... it would take a fair number of vaccinations to vaccinate every hospital person who might be at risk."

Dr Mack said he thought the threat of the spread of smallpox was a small one and he wasn't even in favour of vaccinations for health workers at this stage.

And he said the most likely people to be at risk in a smallpox outbreak in a hospital would be patients, not staff.

But Dr Fauci emphasised that if a threat presented itself, a vaccination policy could be continually developed.

The strategy would be to mobilise people to vaccinate others rather than pre-emptively vaccinate large numbers.

"And there will never be compulsory vaccination I can almost assure you of that, there will only be voluntary vaccination because of the risks of the vaccine," he said.

The Associated Press