After AstraZeneca’s vaccine was linked to an unusual blood clot disorder, Johnson & Johnson’s, based on the same technology, is the target of the same suspicions. What is known about it so far?
What was observed?
In both cases, suspicions arose after tracing several cases of thrombosis in vaccinated humans.
These are not simple thrombosis, such as phlebitis, however very unusual circumstances. First, because of their location: They affect the cerebral veins and to a lesser extent the abdomen, the European Medicines Agency (EMA) said Tuesday of Johnson & Johnson (J&J), after making the same comments about AstraZeneca on April 13. .
These pathologies occur together with a decrease in the number of platelets, so at the same time from blood clots, the patient may have bleeding.
“The treatment for this particular type of blood clot is different from what would normally be administered,” warn the US health authorities, FDA and CDC, which have suspended the use of J&J in the United States.
For the EMA, there is a “possible link” between these rare blood problems and the administration of AstraZeneca and J&J drugs.
The two vaccines are “the likely cause” of these unusual episodes, an FDA official, Peter Marks, estimated a week ago.
The J&J immunizer is authorized in the EU (under the name Janssen), but has not yet been administered. AstraZeneca’s is used in the EU, but has not yet been approved in the United States.
What is this for?
These problems may be related to the technique of both “viral vector” vaccines. This is based on taking another virus for support, which has been modified so that it carries genetic information in the body that can fight COVID.
Both use an adenovirus, a very common type of virus. AstraZeneca is a chimpanzee adenovirus and J & J’s is a human.
“Everything indicates that it is due to the adenovirus vector,” Mathieu Molimard, a French pharmacology specialist, explained on Twitter, recalling that these kinds of problems do not occur with the Pfizer / BioNTech and Moderna vaccines, which contain the messenger RNA. use technique. .
For the time being, it is unknown whether these pathologies are also registered with another vaccine using adenovirus, the Russian Sputnik. This is allowed in about 60 countries, but not in the EU or the United States.
What are the mechanisms?
Several elements point to an over-immune response caused by these vaccines, a “plausible explanation,” said the EMA.
In a study published online March 28, German and Austrian researchers established a comparison with another known mechanism.
The phenomenon “clinically resembles heparin-induced thrombocytopenia (HIT),” said the team of scientists led by Andreas Greinacher from the University of Greifswald.
HIT is an abnormal, serious, and unusual immune response caused in some patients by an anti-coagulant, heparin.
It’s a “plausible explanation,” the EMA ruled on April 7, pushing for new investigations.
What is the risk?
In the case of J&J, there have been eight cases of atypical thrombosis, including one death, all in the United States, under more than seven million doses administered, according to data examined by the EMA.
For AstraZeneca, there were 287 cases in the world, 142 of which were in the European Economic Area (EU, Iceland, Norway, Liechtenstein), the European regulator said Tuesday.
Last week, this body reported 222 cases registered up to April 4 in the European Economic Area and the United Kingdom, among 34 million injections. With a balance of 18 dead through March 22.
But, as with all medications, it’s important to weigh the risks and benefits.
Covid-19 carries a risk of hospitalization and death. The combination of blood clots and low platelets that have been the subject of advice is very rare, and the overall benefits of the Janssen vaccine in preventing Covid-19 are greater than the risks of side effects, ” the EMA concluded Tuesday, as it had previously stated regarding AstraZeneca.
What risk factors are there?
Young women in particular seem to be affected. The eight cases detected with the J&J vaccine involve “people under the age of 60” and “mainly women”. At AstraZeneca, most of the cases involved “women under 60,” according to the EMA.
But it is too early to draw any conclusions. For now, “we have not identified any specific risk factors,” said the regulator for the two drugs.
Despite this, several countries have decided to stop using the AstraZeneca vaccine below a certain age: 30 years in the UK, 55 years in France, Belgium and Canada; 60 in Germany and the Netherlands, and 65 in Sweden and Finland.
These measures are based on a balance of risks and benefits: the older you are, the more likely you are to develop severe covid and the greater the benefit of being vaccinated with AstraZeneca.
The UK authorities released a chart showing that Covid-19 poses a health risk six times greater than the vaccine over the ages of 20-29. But in the 60-69 age group, the risk is 600 times higher.
Norway and Denmark chose to stop using the AstraZeneca vaccine completely.