Australia's COVID-19 vaccination rollout is shifting towards a flu-style program, with all adults who haven't had the virus or a booster in the last six months eligible for another dose.
Health Minister Mark Butler said the government accepted advice from the Australian Technical Advisory Group on Immunisation (ATAGI), and the recommendation would take effect from February 20.
The recommendation for a booster is for people whose most recent COVID-19 vaccine or infection was six months ago or more, irrespective of how many prior doses that person has received.
ATAGI experts have recommended that everyone at risk of severe illness - those aged 65 years and over as well as younger adults who have medical comorbidities, disability or complex health needs - have a booster dose this year.
Asked if Australians should get a booster for every six months they don't have the virus, Mr Butler said the vaccination program was heading in a new direction.
"We're moving to a different stance now based on the advice we have at the moment ... it's very different from previous in terms of that six-month period," he told reporters.
"We're not going to predict the future, but it's true to say internationally the discussion is about looking at a time period. The optimum time period is not yet settled, for now it is six months."
An additional booster will not be provided for under-18s, except where children aged five and older have health conditions that would put them at risk of severe illness.
Omicron-specific mRNA booster vaccines are preferred over other vaccines, with four million doses available now and another 10 million arriving later this month.
Those 10 million doses will mean Australia has its largest vaccine arsenal since 2021 at the height of the pandemic.
Aged-care providers will be encouraged to bring local GPs and pharmacists into their facilities to deliver the booster doses.
With Australia's summer case wave declining, Mr Butler reflected the official caseload of around one million was more likely three million to four million given rampant under-reporting.
Some 2600 Australians lost their lives through that wave.
Chief Medical Officer Paul Kelly said vulnerable people couldn't get complacent and not get their booster shots.
"There absolutely is an effect of having an extra dose of vaccine. The incremental increase in immunity from the vaccine is less each time you have it now because you're continually being boosted by episodes of the virus," he told reporters.
"The vaccine does help, it does work, it does protect people, particularly those at that severe end of vulnerability."
Victorian Premier Daniel Andrews said further expanding the COVID-19 booster jab was not discussed by leaders at national cabinet last week.
He said ATAGI would not have made the decision if it wasn't confident it had the supplies and infrastructure to manage an uptick in demand.
"I'm confident that we'll be able to deliver that," Mr Andrews told reporters in Melbourne.
"And I'm certainly not aware of any unforeseen challenges beyond what's always there when a lot of people want something at the same time."
