EMA finds link between ‘very rare’ but sometimes fatal blood clots and AstraZeneca vaccine
The EMA said Wednesday that very rare but sometimes fatal blood clots should be listed as a side effect for AstraZeneca’s Covid-19 vaccine.
The EMA’s safety committee said the change to the vaccine label is part of an in-depth review of 62 cases of cerebral venous sinus thrombosis (CVST) and 24 cases of splanchnic vein thrombosis reported in the EU drug safety database as of March 22. Eighteen of the cases were fatal.
Despite the rare side effects for the vaccine, known as Vaxzevria, EMA executive director Emer Cooke said in a press conference on Wednesday that the benefits of the vaccine still outweigh the risks.
“The risk of mortality from Covid is much greater than the risk of mortality from these side effects,” Cooke said.
The safety committee said it cannot make any recommendations to reduce the risk of the rare side effects. Sabine Straus, chair of the EMA’s Pharmacovigilance Risk Assessment Committee, said the reported rate of CVST is between 1 and 2 per 100,000 people.
“One plausible explanation for the combination of blood clots and low blood platelets is an immune response, leading to a condition similar to one seen sometimes in patients treated with heparin,” EMA said.
As of April 4, EMA said a total of 169 cases of CVST and 53 cases of splanchnic vein thrombosis were reported to the database, among 34 million people who have been vaccinated with in the EEA and UK. By comparison, Straus noted that for the J&J vaccine, 3 CVST cases were found among 4.5 million vaccinated in the EU/EEA, for Pfizer, 35 CVST cases worldwide were found and 54 million received the vaccine in the EEA, and for Moderna, 5 CVST cases worldwide were among 4 million vaccinated in the EEA.
“EMA is reminding healthcare professionals and people receiving the vaccine to remain aware of the possibility of very rare cases of blood clots combined with low levels of blood platelets occurring within 2 weeks of vaccination. So far, most of the cases reported have occurred in women under 60 years of age within 2 weeks of vaccination. Based on the currently available evidence, specific risk factors have not been confirmed,” the agency said.
Separately on Wednesday, the UK’s medicines regulator MHRA announced that those under the age of 30 should not receive the AstraZeneca vaccine. As of March 31, 20.2 million doses of the AstraZeneca vaccine had been administered in the UK, meaning the overall risk of these blood clots is approximately 4 people in a million who receive the vaccine, the MHRA said.
AstraZeneca said in a statement that it “has been actively collaborating with the regulators to implement these changes to the product information and is already working to understand the individual cases, epidemiology and possible mechanisms that could explain these extremely rare events.”
The World Health Organization added in a statement, “Based on current information, a causal relationship between the vaccine and the occurrence of blood clots with low platelets is considered plausible but is not confirmed. Specialised studies are needed to fully understand the potential relationship between vaccination and possible risk factors.”