Australians are being urged to get vaccinated against influenza, as doctors say the laboratory-confirmed cases this year are only the tip of the iceberg.

Australia could be in for its worst flu season on record but doctors say it's not too late to get vaccinated.

From January to the end of May, there have been 9132 laboratory-confirmed cases, up 47 per cent compared with the same period last year, which had the highest number since the current form of recording began in 2001.

"This year has all the hallmarks of a severe season," Influenza Specialist Group (ISG) chairman Dr Alan Hampson told a media briefing on Thursday.

"Because we expect the season to peak in August or September, there is still a window of opportunity for people to be vaccinated, particularly groups at real risk of severe outcomes."

He said there had been a high number of deaths and hospitalisations in the northern hemisphere after severe flu outbreaks over their winter.

There had previously been a delay in the vaccine's supply because of a change in the formula, but the ISG's Dr Rod Pearce said it was easily available in Australia now.

People at risk of flu complications, including Aborigines, pregnant women, those with existing medical conditions and over 65s, are eligible for free shots.

Dr Pearce also urged healthy people, who were just as likely to get the flu, to get a vaccination, which took up to 14 days to kick in.

As well as causing direct and indirect deaths, the flu has massive ramifications on hospital emergency departments, the overall health bill and on productivity in the workforce.

Dr Hampson said laboratory-confirmed cases were only the tip of the iceberg, and that up to 15 per cent of Australians were estimated to get the flu each year.

FLU FACTS:
* Causes up to 3500 deaths, 18,000 hospitalisations and 300,000 doctor consultations a year
* Most infectious in the two or three days before symptoms show up
* Can spread up to 2.5 metres through droplets from coughing, sneezing and even speaking
* Wash your hands often, and if you haven't disinfected them, avoid touching your mouth and eyes
* Get vaccinated, the most effective protection.