Updated safety advisory – rare and unusual blood clotting syndrome (thrombosis with thrombocytopaenia)
To date, one case of thrombosis with thrombocytopenia reported in Australia has been assessed by the Vaccine Safety Investigation Group (VSIG). The VSIG is an independent expert advisory group comprising experts in vaccine safety, public health, vaccine confidence and relevant medical specialists in blood disorders, immunology, gastroenterology, infectious diseases, convened by the TGA to assess such cases. The VSIG concluded that, based on available data, there was insufficient evidence to firmly confirm that the clot was caused by the vaccine, but emerging evidence suggests a likely association. However, this conclusion will be reviewed as further information becomes available.
The TGA is carefully reviewing all Australian reports of blood clots following the AstraZeneca vaccine, and are requesting further information from reporters where needed. Any further suspected case will be referred to the VSIG for assessment.
The TGA has also been in regular contact with overseas regulators on the subject. Over the last two evenings we attended the European Medicines Agency (EMA) Pharmacovigilance Risk Assessment Committee (PRAC) meeting which discussed the risk of rare and unusual blood clotting issues in adults who have received the AstraZeneca COVID-19 vaccine. The issue was also discussed several times over the last few days by TGA with the UK Medicines and Health products Regulatory Agency (MHRA) and Joint Committee on Vaccines and Immunisation (JCVI), which advises UK health departments on immunisation.
The EMA has found that there is a possible link between the AstraZeneca COVID-19 vaccine and very rare cases of unusual types of blood clots with low platelets, with most case reports in women under 60 years of age, within 2 weeks of vaccination. Blood clots occurred in veins in the brain (cerebral venous sinus thrombosis, CVST) and abdomen and in arteries.
The EMA PRAC reviewed 86 cases reported as of 22 March 2021 (62 CVST and 24 of other thromboses with thrombocytopenia), 18 of which were fatal. PRAC noted that in Europe and the UK about 25 million people had received the AstraZeneca vaccine. They stated that “the reported combination of blood clots and low blood platelets is very rare and the overall benefits of the vaccine in preventing COVID-19 outweigh the risks of side effects”.
The UK regulator (MHRA) issued new advice on the afternoon of 7 April (UK time) concluding “a possible link between COVID-19 vaccine AstraZeneca and extremely rare, unlikely to occur blood clots”. The MHRA reviewed 79 UK cases of thromboses accompanied by thrombocytopenia reported as of 31 March 2021 (44 CVST and 35 of other thromboses), with 51 of these case reports in women. There were 19 deaths.
MHRA reported that by 31 March 2021, 20.2 million doses of the COVID-19 Vaccine AstraZeneca had been given in the UK, meaning that the overall risk of the rare blood clots was approximately 4 people in a million who receive the vaccine.
The TGA and Australian Technical Advisory Group on Immunisation (ATAGI) are continue to urgently review this information and other data as part of our enhanced safety monitoring of COVID-19 vaccines.
ATAGI met today to discuss the Europe and UK advice in the Australian context. ATAGI has recently published information about the potential risk of blood clots following immunisation with COVID-19 vaccines for consumers and health professionals. The advice includes information about symptoms that might prompt further action and how they can be managed and treated (such as seeking medical attention). This evening, ATAGI released updated advice.
The TGA encourages health professionals and consumers to report suspected side effects following immunisation with COVID-19 vaccines. Every report is valuable and contributes to our safety monitoring.
The TGA has worked with AstraZeneca to update the Product Information for the vaccine to include the latest information about the risk of very rare cases of thrombosis (blood clots) with thrombocytopenia (low blood platelet count). An updated Product Information, effective 8 April 2021 is available on the TGA website. Further updates are under consideration in light of international developments and the most recent ATAGI advice.