Australia had previously said it would offer a Covid-19 booster to everyone over 18 and who had their second dose of the vaccine six months prior.
But with rising cases of the Omicron variant, Australia's Health Minister Greg Hunt said the time interval will be shortened to five months after the second dose.
"A booster dose, five or more months after the second dose, will make sure that the protection from the primary course is even stronger and longer lasting and should help prevent spread of the virus," Hunt said in an emailed statement.
Australia will use both vaccines from Pfizer and Moderna in its booster program.
Australia is one of the most vaccinated countries, with about 90 percent of people over 16 fully inoculated.
Still, Australia said on Saturday it found 1,753 Covid-19 cases in the past 24 hours, up about 3% in the last week and the highest daily total since Oct. 29.