Australia's troubled coronavirus vaccine rollout could spill into next year despite a fresh injection of 20 million more Pfizer doses.
Health supremos have recommended not administering the AstraZeneca vaccine to people under 50 because of an extremely rare but serious blood clot side effect.
It means the immunisation program is unlikely to be completed until 2022, well after the Morrison government's October target.
Prime Minister Scott Morrison refused to say whether all Australians would be offered at least one dose by Christmas.
"We're not in a position at the moment to reconfirm a timetable," he told reporters in Canberra on Friday.
The latest delay is likely to have major implications for ongoing restrictions including international travel and social distancing measures.
An extra 20 million doses of the two-shot Pfizer vaccine have been secured taking Australia's total supply to 40 million.
The additional vaccines are not due to arrive until the final three months of the year.
Just 870,000 doses of the initial 20 million Pfizer jabs have arrived in the country since February.
Health Minister Greg Hunt said supply rates would be stepped up significantly in coming months but declined to reveal numbers at the company's request.
Mr Morrison stressed there was no ban on AstraZeneca jabs for people under 50 with the vaccine recommended for people over that age.
"The AstraZeneca vaccine remains a critical component of Australia's vaccination program," he said.
"My mum is getting it in a couple of weeks."
Labor has lambasted the government for failing to secure more deals with other vaccines successfully being rolled out to millions of people worldwide.
Opposition Leader Anthony Albanese described the rollout as a debacle and demanded certainty about when Australians would be vaccinated.
"This government has failed. This government couldn't run a choko vine up a back fence," he told reporters in Sydney.
The government's immunisation advisory group made the cautious call on AstraZeneca after blood clots mostly in younger people were linked to the vaccine.
The reaction has appeared in four to six people for every million to receive the jab, with a 25 per cent death rate for people who develop the syndrome.
A man in his 40s who was admitted to hospital in Melbourne is the only person in Australia to develop the problem.
People under 50 can still be administered the AstraZeneca jab if a doctor decides benefit outweighs risk.
The government has also agreed to release daily vaccination data after coming under fire for jab numbers trickling out every few days.
The prime minister said vaccinating the most vulnerable people would put the nation on a path to being able to treat coronavirus like the flu.
AstraZeneca noted Australia's decision factored in having no community transmission of the virus.
"Overall, regulatory agencies have reaffirmed the vaccine offers a high-level of protection against all severities of COVID-19 and that these benefits continue to far outweigh the risks," the company said in a statement.