After AstraZeneca’s vaccine began to be linked to an atypical blood clot condition, Johnson & Johnson’s, based on the same technology, is the target of the same suspicions. What is known so far in this regard?
What was observed?
In both cases, the suspicions arose after detecting several cases of thrombosis in vaccinated people.
These are not simple thrombosis, such as phlebitis, but very unusual conditions. First, because of its location: it affects the cerebral veins and to a lesser extent, the abdomen, the European Medicines Agency (EMA) said on Tuesday about Johnson & Johnson (J & J), after making the same comments on 13 April on AstraZeneca.
These pathologies occur at the same time as a drop in the level of blood platelets, so at the same time of blood clots, the patient may suffer hemorrhages.
“The treatment of this particular type of blood clot is different from what would normally be administered,” warn U.S. health authorities, FDA and CDC, which suspended the use of J&J in the United States.
For the EMA, there is a “possible link” between these uncommon blood problems and the administration of AstraZeneca and J&J drugs.
The two vaccines are “the probable cause” of such atypical episodes, FDA official Peter Marks said a week ago.
The J&J immunizer is authorized in the EU (under the name Janssen), but has not yet been administered. AstraZeneca is applied in the EU, although it does not yet have approval in the United States.
What is it due to?
These problems could be related to the technique of the two “viral vector” vaccines. This is based on taking as a support another virus, which is modified to carry in the body genetic information capable of fighting covid.
Both use an adenovirus, a very common type of virus. AstraZeneca is a chimpanzee adenovirus and J&J is a human.
“Everything indicates that it is due to the adenovirus vector,” Mathieu Molimard, a French pharmacologist, explained on Twitter, recalling that this type of problem does not occur with the Pfizer / BioNTech and Moderna vaccines, which use the ‘RNA messenger.
For now, it is unknown whether these pathologies are also recorded with another vaccine that uses 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 a disproportionate immune reaction caused by these vaccines, a “plausible explanation,” according to the EMA.
In a study published online on March 28, German and Austrian researchers established a simile with another mechanism already known.
The phenomenon “clinically resembles heparin-induced thrombocytopenia (TIP),” said the team of scientists led by Andreas Greinacher of Greifswald University.
TIP is an abnormal, severe, and unusual immune reaction triggered in some patients by an anticoagulant drug, heparin.
It’s a “plausible explanation,” the EMA assessed on April 7, urging new studies to be conducted.
What is the risk?
In the case of J&J, eight atypical thrombosis cases have been reported, including one death, all in the United States, among more than seven million doses administered, according to data examined by the EMA.
For AstraZeneca, 287 cases have been counted in the world, of which 142 in the European Economic Area (EU, Iceland, Norway, Liechtenstein), the European regulator said on Tuesday.
Last week, this body reported 222 cases registered as of April 4 in the European Economic Area and the United Kingdom, between 34 million injections. With a balance of 18 dead until March 22.
But, as with all medications, the key is to weigh the risks and benefits.
“Covid-19 carries a risk of hospitalization and death. The combination of blood clots and low platelets that has been warned is very rare, and the overall benefits of the Janssen vaccine in preventing covid- 19 are higher than the risks of side effects, ”the EMA concluded on Tuesday, as it had previously said in relation to AstraZeneca.
What are the risk factors?
Young women seem especially affected. The eight cases detected with the J&J vaccine concern “people under 60,” and “mostly women.” At AstraZeneca, much of the cases were given to “women under the age of 60,” according to the EMA.
But it is too early to draw conclusions. For now, “we have not identified any specific risk factors,” the regulator commented for the two drugs.
However, several countries decided to stop using the AstraZeneca vaccine below 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.
These measures are based on the balance between risks and benefits: the greater it is, the more likely it is to develop a severe form of covid, and the more benefits it entails from vaccinating with AstraZeneca.
UK authorities released a chart showing that covid-19 poses a health risk six times greater than the vaccine between the ages of 20-29. But in the 60-69 age group, the risk is 600 times greater.
Norway and Denmark chose to completely suspend the use of the AstraZeneca vaccine.