Doctors have been blindsided by a major change to the vaccine rollout, with all Australians aged under 40 now able to request the AstraZeneca jab from their GP.
State premiers are also reluctant to endorse the decision, which Scott Morrison announced after a meeting of national cabinet.
The prime minister said the Commonwealth would provide GPs indemnity cover so they could administer AstraZeneca to all adults, regardless of age.
Anyone willing to talk it through with their doctor could therefore get the AstraZeneca jab.
People aged under 50 will be able to use Medicare for a vaccine consultation with a doctor, bringing them in line with older Australians.
Health Minister Greg Hunt said the medical advice had not changed - AstraZeneca remained the preferred vaccine for people aged over 60 and Pfizer was recommended for those under 60.
Mr Hunt argued the only change was making AstraZeneca available in more locations.
However, it is clear this decision was not universally supported.
Queensland Premier Annastacia Palaszczuk believes governments should follow the advice of an expert panel known as ATAGI, which recommended AstraZeneca only be given to people aged over 60.
NSW Premier Gladys Berejiklian is also lukewarm about the shift in position.
Ms Berejiklian confirmed the change was discussed at national cabinet and would be followed in NSW, but barely endorsed the policy.
Victorian Health Minister Martin Foley insisted the AstraZeneca call was not a decision of national cabinet.
His department has written to the federal government seeking further advice.
The head of the Australian Medical Association was given no notice of the decision to make AstraZeneca available to all adults.
"Our recommendation is still really for patients to follow the ATAGI advice," Omar Khorshid told The Guardian.
"Be patient and have the ATAGI-recommended vaccine when it's available. I am certainly still backing the expert advice at this stage."
Dr Khorshid suspects the prime minister made the announcement to provide hope to people in lockdown.
"My guess is they are wanting to provide nervous Australians who are going into lockdown this week with something they can actually do to improve their chances of getting through this and to push the nation's vaccination program forward."
Karen Price from the Royal Australian College of General Practitioners welcomed the change.
Dr Price said as long as people understood the low risk of blood clots, she would have no hesitation giving them the AstraZeneca jab.
Some GPs have been blindsided by overnight change and inundated with booking requests.
They are still working through how much cover the indemnity scheme provides.
"Please remember us GPs are still trying to get our heads around last night's announcement concerning AstraZeneca too and what it means for our patients," Dr Price said.
"A reminder to treat all nurses, receptionists and administrative workers with respect. We are doing our best."
The decision comes as coronavirus outbreaks force a return to lockdowns across the country.
Queensland is the latest jurisdiction to call a three-day lockdown.
Residents of southeast Queensland, Townsville, Palm Island and Magnetic Island will be subjected to the stay-at-home restrictions.
They join millions of people locked down in Perth, Sydney and Darwin.