More than six million flu shots will be free for Australians aged over 65, indigenous people, pregnant women and those at a greater medical risk of contracting the virus.

Health Minister Greg Hunt on Sunday announced a nationwide distribution of the influenza vaccine, available for eligible people at no cost through the federal government-funded National Immunisation Program.

Mr Hunt said it's important Australians get vaccinated each year as the virus changes from year to year.

"Clinical experts have advised that optimal protection against influenza occurs within the first three to four months following vaccination," he said.

"Getting vaccinated from mid-April allows protection during the peak influenza transmission period, from around June to September in most parts of Australia."

Pregnant women can receive their free vaccine at any stage of their pregnancy to protect themselves and their unborn baby or babies.

An enhanced vaccine will again be made available for people aged 65 or over, given 75 per cent of influenza-associated deaths in 2018 occurred within that age bracket, according to government figures.

The NIP provides free vaccines for eligible people against 17 vaccine-preventable diseases including influenza, hepatitis B, whooping cough, measles and the recent addition of meningococcal ACWY for adolescents.

The immunisation rate for five-year-old Aussies is 94.67 per cent, nearing the herd immunity rate of 95 per cent, Mr Hunt said.

He encouraged those over the age of six months to get vaccinated for the 2019 flu season.

A record 11 million Aussies got a flu jab in 2018.

AUSTRALIANS ELIGIBLE FOR THE FREE 2019 INFLUENZA VACCINE

- People aged 65 years and over (enhanced vaccine)

- Pregnant women

- Aboriginal and Torres Strait Islander people aged six months and older

- People aged six months or older with certain medical conditions which put them at risk of severe influenza