Up to 12 million Australians are in lockdown, or are about to be, as four states scramble to contain outbreaks of the highly contagious Delta variant of COVID-19.

The lockdowns in NSW, Queensland, the Northern Territory and Western Australia come amid rising confusion about the latest change to the troubled national coronavirus vaccine rollout.

GPs say they were blindsided by Prime Minister Scott Morrison’s announcement on Monday night that the AstraZeneca vaccine would be immediately available to anyone under 40.

Medical clinics Australia-wide were inundated with booking requests on Tuesday. There are reports of some GPs knocking back requests from people under 40 as they await official advice.

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The head of the Australian Medical Association said doctors had no notice of the abrupt decision to make AstraZeneca widely available to younger people, which came after Monday’s national cabinet meeting.

Mr Morrison’s announcement came despite there being no change to the Australian Technical Advisory Group on Immunisation’s official advice – that AstraZeneca be given only to those over 60.

“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 suspected Mr Morrison’s announcement was designed to offer 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.”

At his media briefing after national cabinet on Monday night, Mr Morrison said all Australians, no matter their age, would soon be able to get their AstraZeneca jab at GP clinics.

An indemnity scheme would protect GPs from any litigation when administering AstraZeneca to willing Australians.

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Federal Health Minister Greg Hunt later confirmed ATAGI’s advice remained the same.

“There’s no change to the medical advice. There’s simply the opening of that access to those that are under it,” he said.

“As has always been the case … on the basis of informed consent, individual patients and their doctors have been able to make a decision to take up the AstraZeneca on the basis of their individual circumstances and their own judgment.”

Victorian Health Minister Martin Foley said expanding the rollout to those under 40 had not been agreed to at the national cabinet meeting.

“The [state] Department of Health has reached out to the Commonwealth to request advice about the eligibility requirements formally changing,” he said on Tuesday.

Mr Foley urged people aged 18-39 to remain patient.

“If there’s a degree of confusion out there with the GPs as we seek to roll this out – it’s not by anyone in the GPs’ or the state clinics’ planning,” he said.

“As soon as we get all the information and clarification from the Commonwealth, we will implement the system as quickly and as smoothly as we possibly can.”

Victoria’s chief health officer, Brett Sutton, said the state was yet to receive any word of “open eligibility” for the AstraZeneca doses. Health care and quarantine workers in the 18-39-year age group had been eligible for shots for some time.

Earlier, Premier Daniel Andrews welcomed the rollout tweak but noted Victorians aged 18-39 would not be able to walk up for their long-awaited shot at the state’s mass vaccination hubs.

“It’s part of the Commonwealth exclusive side of this,” he told ABC radio on Tuesday.

He will consider broadening the order to Victorian-run centres, if supply can be boosted.

“It’s not about ‘have we got enough nurses, have got enough physical space?’. They’re not limiting factors,” Mr Andrews said.

“The only limiting factor at the moment is, do we have enough supply to get into as many arms as we can as fast as we can?”

NSW Premier Gladys Berejiklian confirmed the change was discussed at national cabinet. She said it would be followed in NSW, but she was lukewarm about the shift.

“At the moment, the health advice suggests if you’re over 60, you should get the AstraZeneca, no questions asked,” she said.

“If you’re 40 years old, you can consult your GP on whether or not to take the AstraZeneca vaccine.”

Queensland Premier Annastacia Palaszczuk said governments should follow ATAGI’s advice.

The state’s chief health officer, Jeannette Young, repeatedly stressed it was Mr Morrison’s idea to offer AstraZeneca to those under 40.

“There are some people asking to get AstraZeneca, although the clinical advice is they should not,” Dr Young said.

But Karen Price from the Royal Australian College of General Practitioners welcomed the change in position.

Dr Price said as long as people understood the low risk of rare blood clots, she would have no hesitation giving a well-informed patient under 40 the AstraZeneca vaccine.

-with AAP