The Therapeutic Goods Administration on Wednesday gave provisional approval for Australians 18 and over to receive a top-up dose of the Pfizer vaccine.
Prime Minister Scott Morrison said the government would finalise plans for the expanded rollout within the next week.
"We'll be starting with those in the aged care facilities like we did with the vaccine program," he told the Nine Network.
People with severely compromised immune systems are already eligible for a third jab but the latest advice paves the way for the general population to receive another shot.
The TGA recommended the booster shot be given at least six months after a person's second dose.
The Australian Technical Advisory Group on Immunisation will provide further advice on boosters to the government shortly.
Leading epidemiologist Mary-Louise McLaws said third shots were proven to work well.
"There's fantastic evidence now that your booster shot really does supercharge your immune system to get that vaccine efficacy up high," she told the Nine Network.
'There are many people who will benefit from this."