The Therapeutic Goods Administration (TGA) has approved Pfizer's paediatric dose of its COVID vaccine for children aged between six months and five years old.
The Australian Technical Advisory Group on Immunisation (ATAGI) is yet to make a decision on which under-fives will be eligible.
Pfizer is the second vaccine to be approved for that age group, after Moderna's jab was approved in July.
"This paediatric vaccine is made in the same way as the vaccines for older persons, however, it contains a lower amount of active ingredient (3 micrograms)," the TGA said.
It said it had made the decision after considering data from an ongoing clinical study in the United States that included more than 4,500 participants.
"[The trial] demonstrated that the immune response to the vaccine was similar to that seen in children aged 5 to 12 years," the TGA said.
"The study also showed that the safety profile in children was similar to that seen in adults with observed side effects being mild."
Although ATAGI cleared the Moderna vaccine for the under-fives earlier this year, it recommended it only be given to at-risk children.
That includes children who are severely immunocompromised, have a disability, or complex health conditions that increase the risk of COVID-19.
ATAGI said around 70,000 children fell into those categories.
Pfizer is already approved and in use as a primary dose for children aged five and older, after being given the green light in January.
In July Health Minister Mark Butler flagged that there was a "very limited" supply of paediatric vaccines available.
It is not clear if the government has purchased paediatric doses of Pfizer's vaccine in preparation for its approval by ATAGI.
