H1N1 is swine flu, and the warning comes from the Sydney West Area Health Service.

The service says that children under five are three times more likely to need hospital treatment.

It recommends inoculations with the Panvax vaccine, which was approved for children aged between six months and 10 years last December.

``Panvax is available, free for Australian residents, from their GP,'' the health service's Vicky Sheppeard said.

``We strongly recommend that parents contact their GP or local immunisation clinic to arrange free vaccinations for their children.

``Adults, especially pregnant women and people with chronic illnesses, should also get it.''

Dr Sheppeard said that overseas, more than 200 countries had, between them, reported about 15,000 deaths from swine flu.

``It is likely that there will be an early start to Australia's influenza season,'' she said.

``Being prepared and getting your family vaccinated against pandemic influenza before the season starts makes sense.''

Contact your local GP for more information.