The Therapeutic Goods Administration says 16 and 17-year-olds will be able to get the COVID-19 booster in the same dosage as adults.
A final green light is still needed from Australia's leading vaccine advisory group ATAGI before the boosters are rolled out further.
Currently, only those 18 and older have been able to get the booster.
The medical regulator is still monitoring trials of vaccine boosters for younger children.
The booster decision comes as federal, state and territory leaders debate whether to change the definition of fully vaccinated to require a third dose.
No decision was made on the issue at Thursday's national cabinet meeting, with the Australian Technical Advisory Group on Immunisation continuing to consider the issue.
However, it would be up to individual jurisdictions to update their respective public health orders, should the definition change.
With large numbers of aged care facilities across the country being affected by the Omicron wave of COVID-19, Prime Minister Scott Morrison defended the government's handling of COVID in the sector.
He said about 86 per cent of aged care facilities had received visits for booster shots.
"The balance of those are occurring over the course of the next week, and residents in aged care have been the key focus of the federal government," Mr Morrison told Brisbane radio 4BC.
"I'll be honest, it's a hard challenge dealing with Omicron and (there's staff issues) happening right across the health system."
The prime minister also defended Aged Care Minister Richard Colbeck, after it was revealed he chose to attend the cricket over a COVID-19 committee hearing when 40 per cent of the system was in lockdown.
While Mr Colbeck said he couldn't attend the hearing due to diverting resources away from "urgent and critical work", his register of interests showed he accepted tickets to the Ashes test in Hobart for three days.
Mr Morrison said the minister had had regular contact with the aged care sector.
"Ministers have many responsibilities, I can understand the criticism ... I think Richard has taken that on board," he said.
"I know what he does each and every day or the welfare of people living in our residential aged care facilities, and he'll take the criticism on the chin and he'll get back to work."
Defence Minister Peter Dutton said the possibility of a change in definition of fully vaccinated was for medical experts to decide.
"The main message is just to encourage people to get their booster shot," Mr Dutton told the Nine Network on Friday.
"We want to make sure we have sufficient protection, and it is obvious you need the booster and out of all the data available, people that have the booster shot are less likely to have a more severe case of Omicron."
Labor deputy leader Richard Marles said booster rates remained low across the country.
"Where we stand relative to the rest of the world, we have had a slow rollout of the booster and that comes on the back of a very slow rollout of the vaccine proper last year," he said.
"Other parts of the world are going in that direction (to make three vaccine doses be defined as fully vaccinated) but that is a matter to be listening to the medical advisers."