The groups will include those 65 or older, Indigenous Australians aged at least 50, disability care residents and the immunocompromised.
An estimated 4.7 million people will be eligible to get the fourth dose but its expected less than 200,000 will be able at the start of the rollout.
People can have a second booster shot four months after receiving their first.
A parliamentary hearing was told on Friday eligibility numbers will be "relatively small" initially, with the bulk of people more likely able to book vaccination appointments through May and June.
Health department secretary Dr Brendan Murphy says the fourth jab will be critical in the effort to protect at-risk Australians ahead of winter, with a surge in cases of both the virus and influenza looming.
"The single most important thing we can do to protect people with underlying medical conditions, people with disability, people at risk of severe COVID, is to get as much vaccination - including full booster protection - as possible," he said.
The Australian Health Protection Principal Committee expects an infection peak associated will hit in mid-April in several jurisdictions.
Comprised of chief health officers from across the country, the group says it is considering recommending the removal of quarantine for close COVID-19 contacts.
It says isolation could be replaced by frequent rapid antigen testing, mask wearing outside the house and limiting access of close contacts to high-risk settings.
As of Saturday, almost 12,950,000 Australians had received a first booster vaccine. Almost 20 million have had at least their first vaccine shot and roughly 900,000 remain unvaccinated.
More than 54,000 COVID-19 infections and 26 virus-related deaths were reported across the country on Saturday.
AAP with The Project.