Australians will be able to get COVID booster shots four months after their second jab from early next year.
The change approved by the Australian Technical Advisory Group on Immunisation will apply from January 4.
From the end of January, the interval will change again, with millions of Australians able to get third shots three months after their second dose.
Health Minister Greg Hunt, who announced the changes on Friday morning, said it meant the number of people eligible for boosters would jump from 3.2 million on Friday to 7.5 million at the beginning of January, and then again to 16 million at the end of January.
Chief medical officer Paul Kelly said new evidence about the protection of the vaccine against Omicron was behind the move.
“Just because you get to three months, or four months, or five months, or six months, you do not immediately lose your protection, that’s not the case,” he said.
“It does decrease over time, it remains in place for severe infection but it is diminished for Omicron compared with Delta.”
Friday’s announcement came after days of pushing from some states for the interval between second and third doses to be shortened as the Omicron variant has taken hold and COVID case numbers have spiked.
It also came less than a day after Mr Hunt lashed Opposition Leader Anthony Albanese as “unworthy”, after the Labor leader backed calls for ATAGI to bring the third doses forward.
“Utterly irresponsible. Utterly inappropriate. Utterly unworthy of somebody who wants to be a PM,” Mr Hunt said.
On Friday, Mr Albanese hit back.
“Greg Hunt’s response was quite extraordinary yesterday afternoon … He said, ‘Only a fool would call for it’,” he said.
“Less than 24 hours later, he’s not only called for it, he’s announced it.”
States and territories are reintroducing restrictions and updating how they trace and isolate positive cases as COVID infections soar across the country.
Masks have been mandated across almost every state and territory, including NSW after Premier Dominic Perrottet backflipped on his anti-mandate position on Thursday.
NSW will also reintroduce QR codes in all settings from December 27, when hospitality venues will return to the one person per two-square metre rule.
Victoria has also reintroduced a mask mandate, while Western Australia Premier Mark McGowan followed the lead of the two biggest states after a backpacker tested positive on Thursday after being infectious in the community for several days.
High-risk, large public events in WA have been cancelled and dancing banned, except at weddings.
“I know this is not the news we wanted to hear two days before Christmas, but unfortunately this is the reality of COVID-19,” Mr McGowan said.
Queensland had another virus record on Friday, with 589 new infections, while the ACT had 102 and has already updated its definition of close contacts. Tasmania reported a record 27 new cases, and South Australia 688.
The Northern Territory had 10 infections on Thursday, and is yet to give a Friday update.
There are also growing calls for the federal government to make rapid antigen tests available for free amid concerns of more infection spikes over the Christmas break.
The NSW government plans to make rapid antigen tests free to residents, to ease congestion at overwhelmed PCR testing sites.
Long queues at testing clinics across the country this week have prompted calls for a rethink of entry requirements in states such as Queensland, which demands a negative PCR test prior to arrival.
Queensland will move to allow rapid antigen tests ahead of travelling, but not before January 1.
Mr Albanese wants the federal government to do more on rapid testing.
“I don’t think anyone should be excluded from getting a rapid antigen test because of their income,” he said.
The federal government has introduced free rapid testing measures for residential aged-care, but has resisted doctors’ calls to make the tests free universally.