The European Medicines Agency – which has said the benefits outweigh the risks, so the vaccine should remain in use – will provide an updated assessment next week.
What has been observed?
Blood clots seen in a handful of people vaccinated with AstraZeneca are described by the French Medicines Agency (ANSM) as “very atypical”.
“This thrombosis of the great veins is located in an unusual way in the brain and, more rarely, in the digestive tract,” commented the agency.
It is also associated with a condition characterized by abnormally low levels of platelets, which are small pieces of cells in our blood that form clots to stop or prevent bleeding.
In mid-March, Germany’s drug regulator, the Paul Ehrlich Institute (PEI), was the first national health authority to point out what it described as an aberrantly high number of cases related to these rare brain blood clots, mainly in young and middle-aged women.
According to some specialists, this set of symptoms pointed to the so-called disseminated intravascular coagulation (DIC), in which blood clots form throughout the body.
Also seen in extreme cases of sepsis, this condition involves “both thrombosis and bleeding,” Odile Launay, a member of the scientific body that advises the French government on Covid-19 vaccines, told AFP.
Link to the vaccine?
“A causal link with the vaccine has not been shown, but it is possible, and further analysis is underway,” the EMA said last week.
The agency is scheduled to meet on the issue April 6-9.
Other specialists were more categorical.
“We have to stop speculating whether there is a link or not; all cases showed these symptoms between three and ten days after inoculation with the AstraZeneca vaccine,” said Pål Andre Holme, who leads a team at Oslo National Hospital that works in these cases. He said Norwegian media.
“We have not found any other triggers.”
Norway national drug agency he backed this assessment, with one of his executives, Steinar Madsen, saying that “there is probably a link to the vaccine.”
For its part, the ANSM of France, which notes “the very unusual type of thrombosis, a similar clinical profile and a similar time of onset”, said there was a “small” risk.
How big is the risk?
As of March 31, the EMA had identified 62 cases of cerebral venous sinus thrombosis (CVST) in the world, 44 of them in Europe, among 9.2 million doses of AstraZeneca administered.
Of these, 14 have resulted in death, although it is not possible to definitively attribute the deaths to this rare form of thrombosis, EMA Director Emer Cook said last week in a video conference.
The statistics, he added, are complete or close to that.
In Germany, there have been 31 suspected CVST cases, 19 accompanied by a decrease in blood platelets, with nine deaths, according to the Paul-Ehrlich Institute.
These cases were spread over 2.8 million doses of AstraZeneca vaccine injected, or just over one case per 100,000 doses.
Comparable figures for France are 12 cases and four deaths from 1.9 million doses, and for Norway, five cases and three deaths from 120,000 doses.
Britain, where AstraZeneca has been administered more than any other country, recorded 30 cases as of Saturday, including seven deaths, in a total of 18.1 million doses.
But as with all medications, the risks must always be weighed against the benefits.
“We would all prefer to have drugs that are 100 percent safe, but they don’t exist,” Adam Finn, a professor of pediatrics at the University of Bristol, told the London newspaper. Science Media Center last week, commenting on renewed AstraZeneca vaccine bans in Germany and elsewhere.
“Right now, the greatest risk to our lives and livelihoods around the world is Covid-19,” Finn added. “We need to stay focused on the need to prevent millions more human lives from being claimed before it is under control and the only effective way to do that is through vaccination.”
The EMA has consistently echoed this view. “The benefits of the AstraZeneca vaccine in preventing Covid-19, with its associated risk of hospitalization and death, outweigh the risks of side effects,” he said in a statement on March 31.
Most cases of cerebral thrombosis have occurred in those under 65 years of age, but it is impossible to draw any conclusions about age because the vaccine has been administered to date mainly among younger populations.
The fact that the majority of cases were among women may simply reflect the fact that priority was given to the health sector, predominantly women.
“At present, the review has not identified any specific risk factors, such as age, gender or a prior medical history of bleeding disorders for these very rare events,” the EMA said.
However, after some countries temporarily stopped the AstraZeneca jab in mid-March, several countries have stopped the vaccine again.
Germany decided last week to ban its use for anyone under the age of 60, while in Canada, as in France, the age limit is 55. In Sweden, the age limit is 65 years.
“We don’t have just one vaccine, we have several”, Sandra Ciesek, professor of medical virology at the Goethe University in Frankfurt, wrote in Science magazine.
“So restricting the AstraZeneca vaccine to older people makes sense to me.”
Norway and Sweden have taken the most radical step of completely stopping the AstraZeneca vaccine.
However, on March 25, Sweden said it would restart vaccines against AstraZeneca in those over 65 this week.
At the moment, there are only hypotheses, although the EMA is expected to suggest next week which are the most likely.
in a study published on March 28 As yet to be peer-reviewed, German and Austrian researchers pointed to a known biological mechanism as a possible explanation for the apparent increase in atypical thrombosis.
The AstraZeneca vaccine, they wrote, is associated with a thrombosis disorder “clinically resembling heparin-induced thrombocytopenia (HIT).”
HIT is a rare and serious immune system reaction to the blood thinning drug heparin.
The authors, led by Andreas Greinacher of the University of Greifswald, came up with a name for what they described as a new syndrome: “vaccine-induced prothrombotic immune thrombocytopenia (VIPIT).”
Researchers at Oslo National Hospital had previously suggested that the cases could have been caused by a “strong immune response” to the vaccine.
An association of French scientists and doctors called “On the side of science” has said that such an immune response could come from accidentally inserting the needle into a vein in the upper arm, rather than a muscle.
George is Digismak’s reported cum editor with 13 years of experience in Journalism