Following the latest advice from the Australian Technical Advisory Group on Immunisation, people over 16 years who have received a COVID-19 booster will be considered "up to date".
But those who got their second dose more than six months ago and are yet to get their booster will be considered "overdue".
The updated advice from the advisory group will come into effect at the end of March.
People aged over 16 are eligible for their booster shot three months after receiving their second dose.
However, it will be up to states and territories to mandate boosters for international tourist arrivals.
Overseas tourists will only be required to have two doses of a vaccine to enter the country, when the borders open up on February 21.
Defence Minister Peter Dutton said while the vaccination requirements had changed, it was important to listen to the medical experts.
"The reality is that circumstances change as the medical advice comes along," he told the Nine Network on Friday.
"That's the reality of (expert) advice as they learn more, as there are further studies and larger sample groups - they will do whatever's the safest in their judgement and that's the advice that you act on."
Labor deputy leader Richard Marles said booster shots were critical for people.
"It's clearly important to get us through this and that is the evidence we're seeing from around the world," he said.
"It makes sense to me that you need a booster shot if you're going to be working in aged care, but the fundamental point here is people need to be going off and getting their booster."
It comes as there were 46 new deaths from COVID-19 in the latest reporting period.
Of those, there were 19 fatalities in NSW, 14 in Queensland and 13 in Victoria.
The latest figures showed there were 24,000 infections across the country, with almost 9000 in both NSW and Victoria, while Queensland had just under 6000 cases and Tasmania had 552.
Prime Minister Scott Morrison, premiers and chief ministers agreed during Thursday's national cabinet meeting that only aged care workers would be subject to a blanket booster mandate.
The sector has recorded more than 500 virus deaths this year.
The federal government has thrown a task force and bonus payments at the problem as workers request a 25 per cent pay rise.
Clinical epidemiologist Nancy Baxter said the new advice on vaccine doses was sensible.
"Years from now, when people get the COVID vaccine for the first time, they will think of this actually as a three-dose vaccine, that you need three doses to actually be vaccinated," she told the ABC.
"It is more likely than not that we will be facing another variant ... so I do think it's important that our language now starts to reflect that we're not back to normal."
At the latest national cabinet meeting, NSW, Queensland and Victoria agreed to work on a plan to revitalise the cruise ship industry for when the Commonwealth scraps biosecurity controls.
But the precise timing of the restart will be up to individual jurisdictions.
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