For those over 50, Health Department secretary Professor Brendan Murphy said AstraZeneca was strongly recommended.
“It is a vaccine that is very, very effective,” he said.
ATAGI spent hours on Thursday considering the medical evidence. It then issued new advice on the AstraZeneca vaccine, which it provided to the government just after 7pm.
The medical experts made three recommendations, including that AstraZeneca was preferred in adults over 50, after a lengthy meeting. They also recommended adults under the age of 50 should only be given AstraZeneca where the benefits clearly outweighed the risks. Third, it recommended that adults under 50 who had already received their first doses without experiencing serious side effects could safely be given their second dose.
Professor Kelly stressed the data on the rare clotting side effect, venous thromboembolism, was still only preliminary.
“There are very few cases of this extremely rare event that have happened anywhere in the world, but the ones we’ve seen, there’s definitely a tendency for the younger people [to develop it],” he said.
The UK regulator has decided to offer an alternative vaccine for those aged under 30.
Australia has purchased 20 million doses of the Pfizer vaccine and has been relying on the AstraZeneca vaccine as the workhorse of the rollout. The country is expecting its first deliveries of the Novavax vaccine, pending regulatory approval, some time in the fourth quarter of the year.
Late on Thursday, Australian pharma giant CSL said “it remains committed to meeting its contracted arrangements with the Australian government and AstraZeneca for locally produced AstraZeneca COVID-19 vaccines.”
AstraZeneca Australia added that it respected the decision outlined by the government.
“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.” a spokeswoman for the company said.
Earlier, the Prime Minister said the risk of severe side effects with the AstraZeneca vaccine is much lower than with common drugs including paracetamol and the oral contraceptive pill.
Mr Morrison said it was important to know the risk of developing venous thromboembolism was much lower following the AstraZeneca vaccine than the risk of death from COVID-19.
“Let’s note that in the UK, the advice is that some 6000 people’s lives have already been saved by this very vaccine. So we need to consider the positive benefits,” he said.
From UK data, the risk of venous thromboembolism following the vaccine was about one to five per million people.
“To put that in some sort of perspective, the combined oral contraceptive pill, that can include adverse side effects of venous thromboembolism – that’s seven to 10 per 10,000,” Mr Morrison said.
The advice has been shared with the expert medical panel, the Australian Health Protection Principal Committee, which comprises all state and territory chief health officers and led by federal Chief Medical Officer Professor Paul Kelly.
The matter will also be discussed in national cabinet on Friday and in meetings with state and territory health ministers, who were due to meet on Thursday night to discuss the revised advice and its implementation.
On Wednesday 75,880 doses of the Pfizer and AstraZeneca vaccines were administered across the country, Scott Morrison said, taking the national total to 996,214 doses administered so far during the rollout.
The states and territories have administered 509,802 doses. Through the federal government, 486,343 doses have been administered, including more than 125,260 through aged care.
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Rachel Clun is a federal political reporter at The Sydney Morning Herald and The Age, covering health.