Australia’s chief vaccine safety body has issued new advice affirming the safety of the AstraZeneca COVID-19 vaccine for people with a history of many blood clotting disorders.
But the Australian Technical Advisory Group on Immunisation also added two specific conditions to the list of health issues that should trigger a preference for the Pfizer vaccine.
In a joint statement released on Sunday, ATAGI and the Thrombosis and Haemostasis society of Australia and New Zealand (THANZ) said there were “no known markers for increased risk” from the vaccine.
A full list of the TGA’s latest advice on clotting related conditions and which vaccine to receive can be found below.
Specifically, Australians who have a family history of blood clots or incidences of deep vein thrombosis do not have a higher chance of vaccine-induced thrombotic thrombocytopenia – or TTS – occurring after receiving an AstraZeneca dose.
“TTS is a rare condition with a different mechanism to most other causes of thrombosis and/or thrombocytopenia,” ATAGI said in a statement.
“Among case reports, there are no known markers for increased risk for TTS.”
ATAGI was careful to point out that TTS “is a very rare potential complication” and that vaccination remains the best way to prevent severe illness from COVID-19.
“People who choose to delay vaccination until a vaccine other than AstraZeneca COVID-19 vaccine is available should be aware they may not be protected against COVID-19 for months,” the statement reads.
“The risk of potential outbreaks of COVID-19 is ever-present. The Australian population remains largely unimmunised and susceptible to COVID-19 risks.”
Currently, almost 3.6 million COVID-19 vaccines have been administered to Australians.
To date there have been 24 reports of blood clot cases in Australia relating to the AstraZeneca vaccine.
Two doses of AstraZeneca or Pfizer vaccine ‘highly effective’ against Indian strain: UK study
The study found that from April 5 to May 16, two doses of the Pfizer vaccine was 88 per cent effective against the strain and a similar dosage of the AstraZeneca vaccine was 60 per cent effective.
“The difference in effectiveness between the vaccines after two doses may be explained by the fact that rollout of second doses of AstraZeneca was later than for the Pfizer-BioNTech vaccine, and other data on antibody profiles show it takes longer to reach maximum effectiveness with the AstraZeneca vaccine,” the researchers write.
“As with other variants, even higher levels of effectiveness are expected against hospitalisation and death.”
The following groups of people can receive COVID-19 vaccine AstraZeneca:
- People with a past history of venous thromboembolism in typical sites, such as deep vein thrombosis or pulmonary embolism
- People with a predisposition to form blood clots, such as those with Factor V Leiden, or other non-immune thrombophilic disorders
- People with a family history of clots or clotting conditions
- People currently receiving anticoagulant medications
- People with a history of ischaemic heart disease or cerebrovascular accident
- People with a current or past history of thrombocytopenia.
Pfizer is preferred for anyone with:
- A past history of cerebral venous sinus thrombosis (CVST)
- A past history of heparin-induced thrombocytopenia (HIT)
- A past history of idiopathic splanchnic (mesenteric, portal and splenic) venous thrombosis
- Anti-phospholipid syndrome with thrombosis
- People with contraindications to COVID-19 Vaccine AstraZeneca