Researchers at the University of Oxford, the same university that helped develop drug company
vaccine, found that the rare blood clotting known as cerebral venous thrombosis occurred in four in a million people receiving the vaccines from drug company
That compares to five in a million people after the first dose of the AstraZeneca-Oxford vaccine, they said.
In both cases, the risk of blood clots is much higher in those who contract the Covid-19 virus. CVT occurred in 39 in a million patients, the researchers said.
“We’ve reached two important conclusions. Firstly, Covid-19 markedly increases the risk of CVT, adding to the list of blood clotting problems this infection causes. Secondly, the Covid-19 risk is higher than we see with the current vaccines, even for those under 30; something that should be taken into account when considering the balances between risks and benefits for vaccination,” said Paul Harrison, professor of psychiatry and head of the translational neurobiology group at the University of Oxford.
The study has major implications given how regulators have reacted to blood-clot concerns. In Europe, several countries have limited AstraZeneca vaccine use, and the U.S. is now reviewing the vaccine from pharmaceutical
Johnson & Johnson,
which is made using a similar process as the AstraZeneca vaccine and also has triggered blood-clot concerns.
Both the Pfizer and Moderna vaccines are produced with the mRNA process, using the molecules in cells that control protein production to teach the immune system to make coronavirus-fighting antibodies.