People with rare blood clot disorder ‘should not have COVID-19 jab’

Heparin-induced thrombo­cytopenia being investigated as a potential, but unconfirmed, pathway to cases of CVST in Europe.

The Australian Technical Advisory Group on Vaccination has recommended that people with a confirmed history of a rare blood cerebral blood clotting disorder should not be administered COVID-19 vaccines.

The recommendation follows a spate of cases of the rare condition cerebral venous sinus thrombosis in Europe that prompted a host of European countries to suspend administration of the AstraZeneca vaccine.

In its first detailed statement on the issue, ATAGI scientists said the Therapeutic Goods ­Administration had been working with the European Medicines Agency to review data from tens of millions of people given Astra­Zeneca and other COVID-19 vaccines worldwide.

“This shows there is no ­increase in the rates of general thromboembolic disorders after vaccination over expected rates, noting these conditions occur commonly in the absence of vaccination,” the scientists said.

“ATAGI considers there is no evidence of a risk of thrombotic disease after COVID-19 vaccination in people with a history of clotting conditions.”

The advisory group recommended that the AstraZeneca and Pfizer vaccines were safe for ­people with a history of deep vein thrombosis or pulmonary embolism, as well as people with risk factors for thrombosis such as the use of oral contraceptives or smoking, people with low platelets, a history of cardiovascular disease and on anticoagulant medications.

Investigations are ongoing in Europe into 18 cases of CVST — out of more than 20 million vaccines administered — that occurred four to 14 days after the Astra­Zeneca vaccine.

ATAGI said as a precautionary measure, people who had a confirmed medical history of CVST should not have COVID-19 vaccines. It said people with a history of heparin-induced thrombo­cytopenia, an immune-mediated complication of treatment with the drug heparin that affects platelet function, should not have a COVID-19 vaccine. “A HIT-like mechanism is being investigated as a potential, but unconfirmed, pathway to CVST post COVID-19 vaccination,” ATAGI said.

Most of the cases of CVST in Europe, several of which were fatal, affected women aged between 18 and 50 years.

The head of the TGA, John Skerritt, confirmed in a Senate ­estimates hearing the regulator was working with AstraZeneca to update the vaccine’s product information in Australia to warn of a possible small risk of CVST following vaccination, despite no link yet having been established.

“This is not clotting writ large,” Professor Skerritt said. “The number of cases in Europe are really numbering about one to two per million. So these are rare and specialised clotting events.”