Dozens of rare blood clots have been reported amid the tens of millions of AstraZeneca shots that have been administered globally. Data from the European Medicines Agency suggested the risk of blood clots following the vaccine was potentially as high as one in 100,000. Most of the documented cases globally were in people under the age of 55.
A top official at the EMA said on Tuesday there was a casual link between AstraZeneca’s vaccine and the rare blood clotting syndrome, though the nature of the connection was unclear.
“It is becoming more and more difficult to affirm that there isn’t a cause-and-effect relationship between AstraZeneca vaccines and the very rare cases of blood clots associated with a low level of platelets,” Marco Cavaleri, head of health threats and vaccine strategy at the EMA told Rome’s II Messaggero newspaper.
But he said the benefits of taking that vaccine still outweighed the risks. A spokesperson for the EMA said its evaluation had not yet reached a conclusion and the review was ongoing. The EMA’s review is expected to be finalised by Friday.
Britain is reportedly considering restricting the vaccine in younger people. France, Germany, Sweden and Canada are among several countries that have already done so.
Denmark and Norway have completely paused their AstraZeneca rollouts and health authorities across several European countries reported reluctance among citizens to get the shot.
The University of Oxford also paused its clinical trial of the vaccine in children and teenagers while it awaits more data on the blood clotting issue.
Federal Department of Health secretary Professor Brendan Murphy said on Wednesday the Therapeutic Goods Administration and Australian Technical Advisory Group on Immunisation (ATAGI) had advised the government to continue its AstraZeneca rollout considering the benefits of the vaccine outweighed its potential risks.
Professor Murphy said it was difficult to draw conclusions based on one case of blood clotting potentially linked to AstraZeneca in Australia. He added that Australian advisory groups continue to work closely with counterparts in the UK and Europe where there is more data about AstraZeneca.
“That’s what’s going to give us the true picture of whether this is a real problem and whether it has any significance,” Professor Murphy said. “We are taking this matter very seriously at the moment. We are continually reviewing the situation.”
Associate Professor James Wood, UNSW epidemiologist and a member of ATAGI said: “I think at this point experts believe the link is real and it’s more about narrowing down who is at risk, what the level of risk is and what the best clinical advice is around advising patients to monitor for symptoms of concern following immunisation.”
Following the emergence of the Melbourne case, electronic emergency triage records are being analysed across Victoria with experts searching for keywords related to the COVID-19 vaccine and blood clots.
Professor Buttery said in some cases patient admission data may be examined, too.
“Emergency department records are good in that they are very up to date,” he said.
“But as with all these things, it’s more complex. Usually, we only get one diagnosis from the emergency department, whereas if we have access to the admissions data we get all the diagnoses the patients had, which is going to be much more accurate in terms of identifying a rare condition like this.“
A Victorian Department of Health spokesman said the state had a well-established vaccine safety service known as the Surveillance of Adverse Events Following Vaccination. This service is responsible for detecting, reviewing and tracking adverse events.
“This system includes reviewing regular data from hospitals and other clinical settings to establish background rates for adverse events as well as real-time surveillance mechanisms which permit rapid clinical response,” he said.
“Vaccine safety has always been paramount in Victoria.”
ATAGI has urged anyone receiving the AstraZeneca shot to be on alert for severe, persistent headaches that do not settle with paracetamol or other painkillers.
Reports of overseas cases indicate symptom onset was between four and 20 days after vaccination and have generally been severe, with patients requiring hospitalisation.
The threshold for reporting an adverse event is low. Doctors don’t need to suspect the vaccine caused the symptoms to report it and an expert panel reviews all serious adverse events.
The TGA is ultimately responsible for detecting and responding to any vaccine safety concerns and maintains an adverse events database.
NSW Health confirmed it is also searching through its hospital records, but to date there have been no reported cases of the disorder.
A spokesperson for AstraZeneca said patient safety remained their highest priority and the company was working with the TGA and ATAGI as they conducted their assessment of the blood clot case.
Melissa Cunningham is The Age’s health reporter.
Kate Aubusson is Health Editor of The Sydney Morning Herald.
Rachel Clun is a federal political reporter at The Sydney Morning Herald and The Age, covering health.