After the AstraZeneca vaccine started to be associated with an atypical blood clot condition, Johnson & Johnson, based on the same technology, it is the target of the same suspicions. What is known about this so far?
What was noticed?
In both cases, suspicion arose after several cases of thrombosis were detected in vaccinated individuals.
These are not simple thrombosis, such as phlebitis, but very unusual conditions. First of all, due to their location: they affect the cerebral veins and to a lesser extent, the abdomen, the European Medicines Agency (EMA) said on 7 April about AstraZeneca.
With the vaccine Johnson & Johnson “Cerebral venous sinus thrombosis” was also observed, US health authorities, the FDA and the CDC said on Tuesday.
These pathologies appear together with a decrease in the level of platelets in the blood, so that, at the same time with the formation of blood clots, the patient may suffer bleeding.
The EMA first acknowledged on April 7 that these problems could be caused by the vaccine AstraZeneca.
However, this link has not yet been officially established with the vaccine Johnson & Johnson, licensed but not yet administered in Europe under the name Janssen. In the United States, his post was suspended on Tuesday, pending a scientific response.
What is this for?
These problems could be related to the technique of both “viral vector” vaccines. It is based on taking another virus as a support, which is modified to carry genetic information in the body capable of fighting COVID.
Both use an adenovirus, a very common type of virus. Cel al AstraZeneca is a chimpanzee adenovirus and that of Johnson & Johnson it is a human one.
“Everything indicates that it is due to the adenovirus vector,” explained on Twitter Mathieu Molimard, a French pharmacologist, noting that this type of problem does not occur with Pfizer / BioNTech and Moderna vaccines, which use the RNA messenger technique.
It is not yet known whether these diseases are also reported with another vaccine using adenovirus, Russian Sputnik V. It is licensed in about 60 countries but not in the European Union or the United States.
What are the mechanisms?
Several elements indicate an excessive immune response caused by these vaccines against COVID-19.
In a study published online on March 28, German and Austrian researchers made a comparison with another known mechanism.
The phenomenon “clinically resembles heparin-induced thrombocytopenia (HIT),” said the team of scientists led by Andreas Greinacher of the University of Greifswald.
HIT is an unusual, severe and abnormal immune reaction triggered in some patients by an anticoagulant, heparin.
It is a “plausible explanation,” the EMA said on April 7, urging new studies.
What is the risk?
This is the main question. According to EMA figures, as of April 4, 222 cases of atypical thrombosis have been detected after 34 million injections of AstraZeneca in the 30 countries of the European Economic Area (EU, Iceland, Norway, Liechtenstein) and the United Kingdom. With a balance of 18 dead by March 22.
Thrombosis occurred “during the two weeks after vaccination,” according to the EMA.
In case of Johnson & Johnson, US authorities recorded six cases, including one death, in more than 6.8 million doses, and symptoms occurred between 6 and 13 days after injection.
But, as with all medications, the key is to weigh the risks and benefits.
“The overall benefits of the vaccine in prevention COVID-19 outweigh the risks of side effects, “the EMA said AstraZeneca.
What are the risk factors?
At this time, most cases with AstraZeneca appeared in “women under the age of 60,” according to the EMA. The six cases detected in the United States with Johnson & Johnson they were women between the ages of 18 and 48.
But it is too early to draw conclusions. So far, “we have not identified any specific risk factors,” the EMA said AstraZeneca.
After the first wave of suspensions, in mid-March, some countries decided to stop using the vaccine under a certain age: 30 years in the United Kingdom, 55 years in France, Belgium and Canada; 60 in Germany and the Netherlands and 65 in Sweden and Finland.
“We do not have just one vaccine, we have several. Therefore, it seems to me that it makes sense to reserve it for AstraZeneca elderly people, “Sandra Ciesek, a virologist at Goethe University in Frankfurt, told Science.
The British authorities have released an image that shows that COVID-19 has a health risk six times higher than the vaccine at the age of 20-29. But in the 60-69 age group, the risk is 600 times greater.
Norway and Denmark have chosen to completely suspend the use of the vaccine from AstraZeneca.
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