Advice on AstraZeneca changed again

The Pfizer vaccine is now the preferred coronavirus jab for Australians under 60, after medical experts re-assessed the risks posed by the AstraZeneca inoculation.

The Australian government says the new advice balances the risk of developing a rare blood clotting condition after getting the vaccine against the effects of COVID-19.

The AstraZeneca vaccine was linked to a rare blood clotting condition known as TTS, or thrombosis and thrombocytopenia syndrome, earlier this year.

It is extremely rare — in the UK about 14 people per 1 million have developed it after their first dose.

Back in April, the panel of experts that advises the federal government on vaccines, ATAGI, recommended that Pfizer become the preferred vaccine for under-50s due to the increased risk of TTS in younger people.

More data about 50-59 age group

But in the past week, seven out of 12 people in Australia who developed TTS after the AstraZeneca vaccine were in the 50-59 age group.

“That has changed the rate of that particular issue within that age group to the point where the rate is very similar to the under-50s,” Chief Medical Officer Paul Kelly said.

“And so that’s been the key new information that has gone to ATAGI and they’ve based that on the risk-benefit equation, now being the risk outweighing the benefit in that particular age group,” Professor Kelly said.

It is not known why the young people are in particularly affected. Kristine Macartney, the director of the National Centre for Immunisation Research and Surveillance, suggested,

“It may be something to do with the very strong immune response that they experience to AstraZeneca vaccines.

“But it is so rare that, to date, it hasn’t been possible to identify any predictive factors.”

Professor Kelly has previously said the difference is most likely down to the way the immune system responds to the adenovirus contained in the AstraZeneca vaccine.

“Younger people, we know, have a more robust immune system and are likely to have this sort of reaction,” he said in April.

Not a new problem but only risk assessment

So, we haven’t really learned something new — it’s all about the risk assessment.

Every week for the past few months, ATAGI has reviewed the rate of TTS cases connected to the AstraZeneca vaccine.

Back in April, the expert group advised that the Pfizer vaccine be preferred over the AstraZeneca jab in people under 50.

But that recommendation was always subject to change, if the rates of the rare TTS condition changed over time.

“What’s happened over a number of weeks is that the [rate per 100,000] cases in people aged 50 to 59 years has slowly climbed over time,” Professor Macartney said.

“It’s also turned out that some of these cases have been quite severe.

“So we really wanted to review the benefits and risks of vaccines in this age group, and are suggesting that it’s preferential for people aged 50 to 59 to have a Pfizer rather than an AstraZeneca.”

The new cases last week pushed the rate of reported TTS cases in the 50 to 59 age group from 1.9 to 2.7 per 100,000 AstraZeneca doses.

AstraZeneca in other countries

The rules surrounding AstraZeneca vary from country to country.

Federal Health Minister Greg Hunt said Australia’s new advice took into account the low level of COVID-19 in Australia.

“We recognise that this is a conservative position, but relative to Australia’s risk of having COVID,” he said.

“The United Kingdom, for example, has an age range of 40 and above for AstraZeneca, South Korea 30 and above for AstraZeneca, and Germany has no age limits on AstraZeneca for the general product for 18 and above.”

Some countries have no age limit on AstraZeneca.

Should have your second dose

Professor Kelly said AstraZeneca remained a very effective vaccine, and encouraged eligible people to get it.

“The benefit of AstraZeneca in the over 60s remains much higher than the risk of this particularly rare but sometimes serious syndrome [TTS],” he said.

“And so people over 60 should still be rolling out to their GP or wherever they are getting their AstraZeneca vaccine and getting that first dose.”

If you’ve already had your first dose of AstraZeneca and had no complications, the official advice says you should get the same vaccine for your second dose.

“Anyone who has had a first dose of AstraZeneca without a problem should feel very confident to have their second dose and should keep that booking,” Professor Kelly said.

Data from the United Kingdom — which has administered far more vaccines than Australia — shows having an adverse reaction to a second dose of AstraZeneca is extremely rare.

The rate of developing TTS after a second AstraZeneca dose is just 1.5 per 1 million, according to a recent update from the UK government.

About the risk of blood clots from AstraZeneca?

Professor Kelly stressed that although TTS could be serious, it was very rare, and the medical community had a good understanding of how to diagnose and treat it.

If TTS is suspected, doctors investigate platelet counts, clotting factors and run special immune and antibody tests, as well as imaging studies to determine the site and size of any potential clots.

According to the Melbourne Vaccine Education Centre, patients would likely be treated by a specialist haematologist.

The president of the Australian Medical Association, Omar Khorshid, said: “People who have had the AstraZeneca vaccine should not be alarmed by this decision.”

“The risks of serious complications, including clotting, from the AstraZeneca vaccine are very low and Australia is now very good at detecting clots in patients who’ve had the AstraZeneca vaccine,” Dr Khorshid said in a statement.

“More importantly, we have developed very effective protocols and treatments that mean most people fully recover from these complications.”