Australian vaccine experts are cautious, though increasingly convinced the AstraZeneca shot may cause this extremely rare subset of thrombosis with thrombocytopenia.
Professor Jim Buttery, head of epidemiology and signal detection at the Victorian immunisation safety service, said he believed there was evidence of causation, “although not conclusively proven yet”.
Associate Professor James Wood, UNSW epidemiologist and a member of the Australian Technical Advisory Group on Immunisation, said: “I think at this point experts believe the link is real and it’s more about narrowing down who is at risk, what that level of risk is and what the best clinical advice is around advising patients to monitor for symptoms of concern following immunisation”.
Professor Tony Cunningham, director of the Centre for Virus Research at the University of Sydney and one of the country’s leading vaccine experts, said “the evidence is firming that this may be vaccine-associated”.
“But you cannot make that assumption unless you have a clear comparison with background rates in the community. And there are other causes of this syndrome. It is potentially possible we could just be unlucky – because it’s so rare.”
Britain on Thursday (AEST) restricted the vaccine for younger people, a move that has already been adopted in several countries, including France, Germany, Sweden and Canada.
Denmark and Norway have completely paused their AstraZeneca rollouts and health authorities across several European countries reported citizens had been reluctant to get their shots.
The University of Oxford has 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 on Wednesday said the Therapeutic Goods Administration and ATAGI had advised the government to continue its AstraZeneca rollout, considering the benefits of the vaccine outweigh the potential risks.
“But we are continually reviewing the situation,” Professor Murphy said.
He said ATAGI was in regular contact with its UK and EU counterparts to assess the data concerning the blood clotting issue.
“We are taking the matter very seriously,” he said.
A spokesman for NSW Health said there have been no cases of VIPIT among people who have received the AstraZeneca vaccine in the state.
But the state’s emergency departments are searching their digital triage and clinical records for keywords relating to the COVID-19 vaccine and blood clots to identify any patients who may have developed the disorder.
The Public Health Rapid, Emergency, Disease and Syndromic Surveillance (PHREDSS) is a near real-time system that identifies changes in trends of emergency department presentations of specific adverse events.
ATAGI has recommended people who receive the AstraZeneca vaccine be alert to severe, persistent headaches that do not settle with paracetamol or other painkillers.
Reports of overseas cases indicate symptom onset was between day four and 20 post-vaccination and have generally been severe, with patients needing to be hospitalised.
Healthcare workers are required to report all serious or unexpected side effects in vaccinated individuals to the local public health unit under NSW Health’s enhanced surveillance and adverse events reporting guidelines.
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.
An adverse event is considered serious if it causes death or hospitalisation, is life-threatening, results in persistent or significant disability or incapacity, results in a congenital anomaly/birth defect or is an unexpected reaction for that specific vaccine.
If a patient needed any kind of medical intervention to prevent any of those outcomes their condition also falls under the “serious adverse events” classification and should be notified.
The Therapeutic Goods Administration is ultimately responsible for detecting and responding to any vaccine safety concerns and maintains an adverse events database.
In a statement, a spokesperson for AstraZeneca said patients’ 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.
With Rachel Clun and Liam Mannix
Get our Coronavirus Update newsletter
Stay across the news you need to know related to the pandemic. Sent Monday and Thursday. Sign up here.
Kate Aubusson is Health Editor of The Sydney Morning Herald.