European authorities pausing the rollout of the AstraZeneca vaccine after a small number of people developed blood clots is an “overreaction”,

A vial of AstraZeneca vaccine is held up.

European authorities pausing the rollout of the AstraZeneca vaccine after a small number of people developed blood clots is an “overreaction”, according to one leading Australian scientist.

Key points:

  • The European Medicines Agency said there have been 30 cases of clot-related events among 5 million vaccinated people
  • A cluster of blood clots does not mean the vaccine caused them, according to experts and all other potential causes must be investigated, included COVID-19 infection itself
  • More than 11 million people have been vaccinated with the AstraZeneca drug in the UK without evidence of an increase in blood clots

“You can’t ignore these events, but I think it’s an overreaction,” Peter Collignon, an infectious diseases expert from ANU, said.

He said generally there were around 100 cases per 100,000 of blood clots in the general population and that the rate of blood clots from people who had received the AstraZeneca vaccine did not appear to be higher than that.

Professor Collignon said in any mass vaccination program, some people were going to have health issues that were not necessarily a consequence of receiving the vaccine.

“So we are going to see everything from heart attacks, to strokes, to pulmonary embolism, and we need to keep an eye on it but generally, this doesn’t seem to be above what you would expect given that millions of doses have been given out,” he said.

Professor Collignon said there was no evidence of increased blood clots in the phase 3 trials of the AstraZeneca vaccine.

The European Medicines Agency (EMA) said the AstraZeneca vaccine’s benefits continue to outweigh its risk.

“There is currently no indication that vaccination has caused these conditions, which are not listed as side effects with this vaccine,” the EMA said.

“The vaccine can continue to be administered while the investigation of cases of thromboembolic events is ongoing,” it added.

The EMA said there had been 30 cases of clot-related events among the 5 million Europeans who have received the jab.

One person in Austria died from blood clots and another was hospitalized with a blockage in the lung after receiving doses from a particular batch of the AstraZeneca vaccine.

Denmark suspended the shots for two weeks after a 60-year-old woman, given an AstraZeneca shot from a batch used in Austria, formed a blood clot and died, health authorities said.

Some EU countries subsequently suspended this batch as a precautionary measure, while a full investigation by the EMA was ongoing.

Italy also suspended the use of AstraZeneca when two men died in Sicily, however, those shots were not from the Austrian batch.

Norway, Iceland, Estonia, Lithuania, Luxembourg and Latvia have also stopped inoculations with the vaccine while investigations continue.

No biological link between clotting and vaccine

RMIT vaccine expert Kylie Quinn said increased clotting had not come up as a potential issue in the UK rollout of the vaccine.

“Biologically, I don’t know why there would be a link between clots and this specific vaccine,” she said.

Professor Collignon said it was important to monitor the vaccine rollout for any serious side effects, to see if it was above what you would expect to see in the general population.

“Tens of millions of doses of [the AstraZeneca] vaccine have been given around the world, so if there is an association with blood clots, which is doubtful, it is a pretty rare side effect compared to the consequences of getting COVID-19 itself,” he said.

Experts said any apparent cluster of side effects needed to be investigated, but it did not mean the cause was the vaccine itself.

Stephen Evans, a professor of pharmacoepidemiology at the London School of Hygiene and Tropical Medicine, said the sensible approach was to make sure the “benefit and risk balance is in favour of the vaccine”.

“This is a super-cautious approach based on some isolated reports in Europe,” he said.

“The problem with spontaneous reports of suspected adverse reactions to a vaccine are the enormous difficulty of distinguishing a causal effect from a coincidence.

“This is especially true when we know that COVID-19 disease is very strongly associated with blood clotting and there have been hundreds if not many thousands of deaths caused by blood clotting as a result of COVID-19 disease.

‘Safety is our first priority: CMO

Australia’s Chief Medical Officer Paul Kelly said there was “no evidence” the AstraZeneca jab caused blood clots.

“The Australian government is aware of reports some European countries have suspended the use of the AstraZeneca vaccine due to some reports of blood clots in people who have been vaccinated,” he said.

“Safety is our first priority and in a large vaccine rollout like this, we need to monitor carefully for any unusual events so we will find them.

“But we do take them seriously and investigate and that’s what Denmark is currently doing.”

Professor Kelly noted there had been more than 11 million people vaccinated in the UK without evidence of an increase in blood clots.

Prime Minister Scott Morrison said any overseas developments in vaccine rollouts were monitored by the Therapeutic Goods Administration (TGA).

“The batches we distribute here in Australia are tested here by the TGA and we have robust processes,” he said.

“I trust the TGA and the advice they have given me.”

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