The definition of being fully vaccinated could move to three doses within weeks but the government has flagged changing it again ahead of an expected winter COVID wave.
Health Minister Greg Hunt says he expects an announcement on the definition being changed to be made in the coming weeks.
But chief medical officer Paul Kelly said the definition could then move to being "up to date" with COVID shots, as it has with other inoculations, given that fourth doses will soon be vital to protect people.
Some immunocompromised people are already up to their fourth dose, Professor Kelly noted.
"I think that is the parlance we will start to use," he said.
Some countries only accept vaccination certificates for a certain timeframe after the last jab, such as 270 days in Spain.
Professor Kelly also warned another outbreak would likely hit during the colder months and would be complemented by a flu season, the likes of which Australia hasn't seen since the pandemic.
"We are learning to live with this virus, and that means that we have to have realistic expectations of what will happen this year," he said.
"I do believe that we will have another wave of Omicron in winter and I think we will have a flu wave in winter for the first time since the beginning of 2020."
Mr Hunt says the booster will better protect against the Omicron variant as some 370,000 teenagers aged 16 and 17 become eligible for their third COVID-19 jab on Thursday.
The minister has also written to Pfizer to encourage the company to go through the process of making booster shots available to younger teens, but a full application is yet to be lodged with Australian regulatory bodies.
"We are encouraging them to bring that forward ... at the earliest possible opportunity," Mr Hunt told the ABC.
Australia has surpassed 8.4 million booster shots, or just under 70 per cent of those eligible, administering over 200,000 third doses a day.
But a third of people in aged care are yet to receive their boosters despite vaccination teams visiting 99 per cent of all aged care facilities to offer the third dose.
It remains unknown how many of the more than 1100 aged care residents who have died with COVID-19 from December 15 to the end of January had received a booster.
Three in four eligible residents have taken up a booster shot, Mr Hunt said, leaving some 35,000 people who haven't taken it up, on top of about 20,000 who have had fewer than two doses.
Aged Care Services Minister Richard Colbeck tried to play down claims of the aged care sector being in crisis at a parliamentary committee on Wednesday, despite acknowledging the extreme pressure staff and facilities are under.
The denial of a crisis has led to Opposition Leader Anthony Albanese to call for Senator Colbeck to either stand down or be sacked from the ministry.
"He is simply incapable of fulfilling the task of looking after the interests of old vulnerable Australians," Mr Albanese said.
"They deserve dignity and respect. Aged care residents are missing out on showering, are missing out on food and water, are not having their wounds tended to. This is a crisis and it is a crisis on this government's watch."
There were a further 38 COVID-19 deaths in NSW, 35 in Victoria, nine in Queensland and one each in South Australia, Tasmania and the Northern Territory.
The deaths come among 12,632 new infections in NSW, 12,157 in Victoria, 8643 in Queensland, 1583 in SA, 656 in Tasmania and 529 in the ACT.
