The extra supply will not prevent major delays in Australians receiving the vaccine, with no guarantees the country will be fully immunised by the end of the year, let alone the federal government’s original October deadline.

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 said.

The latest delay is likely to have major implications for ongoing restrictions like international travel and social distancing measures.

Prime Minister Scott Morrison welcomed the supply boost after the government backed health advice to avoid people under 50 receiving the AstraZeneca jab because of extremely rare blood clots.

The deal means 40 million Pfizer doses, enough for 20 million people, are due to be shipped to Australia across 2021.

The news came as Queensland’s chief health officer, Jeannette Young, said the Pfizer vaccine now did not need to be stored and transported at ultra-low temperatures, making it easier to be distributed to rural and remote parts of the state.

She said updated studies showed it could be stored for two weeks in a ‘normal’ freezer’.

Young described the securing of an extra 20m doses of the Pfizer shot as “perfect” but insisted that older people who were not at risk of having adverse reactions to the AstraZeneca vaccine continue to make plans to have the jab.

She said current supplies of the Pfizer jab were scheduled to arrive sooner.

“(This) will suit our process of 1B then going into 2A and 2B, which is when we start vaccinating younger people,” she said.

Premier Annastacia Palaszczuk said it remained “business as usual” with the vaccine rollout in Queensland, with the AstraZeneca vaccine continuing to be administered while the state awaits more supply of the Pfizer shot.

Morrison also stressed there was no blanket 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.”

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.

Less than one million doses of the Pfizer vaccine have so far arrived in the country, with supply issues hampering the speed of the rollout.

Pfizer jabs have become far more crucial following the advice around AstraZeneca, which was going to be administered to most Australians.

The extra doses are due to arrive in the final three months of 2021.

Australia broke the one million-dose barrier on Friday – a week after the date the government had committed to administering four million jabs.

Health Minister Greg Hunt said more than 81,000 shots were given in the past 24 hours, the highest daily increase since the program started in late February.