Researchers at Oxford University have found that the risk of a rare type of blood clot is generally low, but higher for people who have been infected with Covid-19 than among people who have received the three vaccines authorized in the UK. – those made by AstraZeneca, Moderna and Pfizer.
The study, available in print on Thursday on the Oxford website before being published in a scientific journal, says the risk of cerebral venous thrombosis or CVD – also known as cerebral venous sinus thrombosis or CVST – after Covid-19 infection is in I swear “100 times higher than normal and several times higher than after vaccination or the flu” in all age groups.
“Covid-19 significantly increases the risk of CVD, adding to the list of blood clotting problems caused by this infection,” said Paul Harrison, a professor of psychiatry and head of the translational neurobiology group at Oxford University.
Oxford University, which developed the AstraZeneca vaccine, said the research comes from a separate part of the university and is not linked to the vaccine team. The data used were obtained from external sources, in particular the European Medicines Agency.
Compared to the risk of clots forming from the three vaccines, the risk of infection is “between 8-10 times higher and compared to the initial value, about 100 times higher for infection,” Oxford said in a statement. the press. According to research, compared to mRNA vaccines – Pfizer and Moderna – the risk of CVD from Covid-19 infection is about 10 times higher. Compared to AstraZeneca, the risk of a CVT from Covid-19 is about eight times higher. Johnson & Johnson Covid-19 vaccine was not included in the analysis.
Using an electronic medical record network of over 500,000 Covid-19 positive cases, 489,871 vaccinated cases and 172,724 influenza cases, the study found that 30% of CVD cases occurred in the under-30 age group. , most exposed to the risk of blood clots.
“Given the balances between the risks and the risk of COVID-19 is higher than with current vaccines, even for those under 30; something that should be taken into account when considering the balances between the risks and benefits of vaccination, ”Harrison added.
Dr Maxime Taquet of Oxford’s Translational Neurobiology Group and a co-author of the study warned that data was still accumulating. Researchers also need to determine whether Covid-19 and vaccines lead to CVD in the same way, she said.
Experts have noted that CVD is so rare that there is limited data even before the pandemic, and data and data sources around Covid-19 vaccines are inconsistent and limited.
“In general, the main finding is that these CVD events are very rare – some in every million people involved – in patients with Covid-19 and in people who have had one of the vaccines – but have been much rarer in people who have a vaccine than people who have had Covid-19, “said Kevin McConway, Professor Emeritus of Applied Statistics at Open University, in a comment to the Science Media Center in the United Kingdom. compared to the risk of people who were not vaccinated and did not have Covid-19 – but I say that the risk of CVT in people who had Covid-19 is about 100 times higher than the risk in the general population. ”
Some information: European and British drug regulators announced last week a “possible link” between the AstraZeneca vaccine and rare cases of blood clots, with the UK announcing it will offer people under 30 an alternative vaccine. Other countries have followed suit and either only offer it to people over a certain age, or they are like Denmark and Norway, abandoning the vaccine altogether. While advising the public to beware of clots, regulators said the benefits of the shooting are still worth the risk. The AstraZeneca vaccine has not been authorized for use in the United States.
Six reports of similar clotting events after vaccination with the Johnson & Johnson single-dose vaccine prompted the U.S. Centers for Disease Control and Prevention and the U.S. Food and Drug Administration to recommend a break in vaccine administration to allow for further investigation.
Six women between the ages of 18 and 48 have developed cerebral venous sinus thrombosis, a clot in the area of the brain that collects and drains oxygen-depleted blood. Blood thinners, the typical treatment for clots, should not be used in such cases. The six reported cases were more than 6.8 million doses of Johnson & Johnson vaccine administered in the United States.
The EU, which relies heavily on the J&J vaccine to strengthen its vaccination launch, has also stopped using the vaccine. The European Medicines Agency is expected to announce a decision next week on the administration of the Johnson & Johnson vaccine.
The WHO said on Thursday that “for now, the risk of bleeding is much higher for someone with COVID-19 than for someone who has received the AstraZeneca vaccine.” WHO Regional Director for Europe Hans Kluge reiterated his recommendation on the AstraZeneca vaccine for all eligible adults, calling it “effective in reducing COVID-19 hospitalization and preventing deaths”.