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.