Explainer: Should under-40s get the AstraZeneca vaccine in Australia?

Under-40s have always been able to ask for the AstraZeneca, but GPs will now have full indemnity if they offer it to patients.

This means the government will pay for any legal fees if patients try to sue their GP for advising them to get the vaccine.

While the Morrison government is looking to increase the country's vaccination rate, experts have said official health advice has not changed.

Over 7.5 million doses of COVID-19 vaccines had been administered in Australia on Tuesday, and just over 7 per cent of the adult population is fully immunised.

General practitioners will now be protected if they let under-40s get the AstraZeneca.

The indemnity cover will encourage GPs to offer the AstraZeneca vaccine, said the ACT president of the Australian Medical Association Walter Abhayaratna.

"That level of certainty that they are covered for the unlikely events [of blood clotting], so that GPs can just get on with their jobs, means they are much more likely to be willing and able to help with the rollout," Dr Abhayaratna said.

He said the Australian Medical Association wanted people to get vaccinated, but also understand the risks associated with the AstraZeneca vaccine.

"As long as people are informed and they've had that discussion with their GP, that's best practice," he said.

The health advice hasn't changed, said epidemiologist Professor John Kaldor from the Kirby Institute.

"The recommendation [is] that for medical reasons, the Pfizer is the preferred vaccine for under 60s, but you could always get the AstraZeneca if you had informed consent," he said.

He said what has changed is the government's emphasis on getting more people vaccinated.

That includes reminding younger people they are able to get the AstraZeneca.

A rare condition called thrombosis with thrombocytopenia syndrome - or TTS - can occur when people receive the AstraZeneca vaccine.

Infectious diseases physician Peter Collignon said an abnormal immune response causes the clotting.

An antibody directed at platelets - blood cells that prevent bleeding - is developed.

The platelets become hyperactive, which can create clots.

According to the federal Department of Health, clots occur in about 3.1 per 100,000 cases of under-50 who get an AstraZeneca shot.

That is nearly double the risk than for 60-69 year-olds, where there is blood clotting in 1.4 per 100,000 cases.

In comparison, an estimated 100 in 100,000 people develop clots from the contraceptive pill.

Dr Collignon said developing TTS didn't mean death, as there were therapies which could treat it.

In Australia, the overall fatality rate from TTS is 3 per cent, and only two people have died after having the AstraZeneca vaccine.

There is a one in 1.5 million risk for the second dose.

"It's a very, very rare risk," said Dr Collignon.

"[But young people] need to be aware that for them the benefits versus the risks are different than if you're a 70, 80 year old."

While experts don't know why the risk is higher for younger people, Dr Collignon said it might be because they have a better immune system.

Health experts agreed that over-60s should get vaccinated as soon as possible because of the high risk of serious illness and death if they catch COVID-19.

"Because people over 60 are at a much higher risk the advice is very strongly to be vaccinated sooner rather or later," said Dr Kaldor.

Dr Collignon agreed, adding he thought the risk of dying from Covid outweighed AstraZeneca blood clot risks for over 50s.

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"If you're over the age of 80, you've got a one in 10 chance of dying of Covid. But if you're a 30-year-old your chance is one in 10,000," he said.

"If you've had your first dose and you're over the age of 50, go and get your second dose [of] the AstraZeneca."

For younger people, experts said the choice to get vaccinated with the AstraZeneca depended on their priorities.

"The key thing for a vaccine program is that people have options and can make choices depending on whether they're more concerned about getting a vaccine quickly or waiting for the Pfizer," said Dr Kaldor.

Dr Collignon said community transmission in Australia was currently "very low" and young people could wait for a Pfizer or Moderna vaccine.

Australia is expected to receive 10 million Moderna shots in 2021.

"What is the risk in waiting two or three months until other vaccines become available?" he said.

"If you're a 30-year-old I wouldn't rush and do it unless you feel particularly in a situation where you want it ... [and] are willing to take that risk."

The Therapeutic Goods Administration has not approved any vaccine for under-18s.

Dr Collignon said Australia should wait to ensure it was safe to immunise children.

"My own view is we do not have data on children so we should not vaccinate on children yet," he said.

"Children are at the lowest risk of getting complications, and they don't even seem to spread it much."

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