Pause button.
Vaccination against Covid-19 with the Janssen product was suspended Tuesday in the United States, the time to investigate secondary cases of thrombosis.
The health authorities plan to meet urgently this Wednesday, before a decision expected at the end of the day.
But already, Tuesday afternoon, the Johnson & Johnson group (of which Janssen is a subsidiary) announced "to delay the deployment" of its single-dose vaccine in Europe.
In France, doctors expect the same fate to be reserved for it as AstraZeneca, namely to use it only on people aged at least 55 years.
Decryption.
Why is Janssen suspended in the United States?
The American Medicines Agency (FDA for "Food and Drug Administration") has identified six serious cases of blood clots following injections of the Janssen vaccine.
It is each time a cerebral venous thrombosis, that is to say that one or more cerebral ducts have been "blocked".
All of these patients are women, aged 18 to 48.
One is deceased, another is in critical care.
The suspension of vaccination was decided by principle of "precaution", these six cases do not represent much compared to the nearly 7 million vaccinated with Janssen in the United States.
The people supposed to receive this product in the coming days "should not be worried, because it is a very low risk", assured Tuesday evening the immunologist Anthony Fauci, the "Mr. vaccination" of the American president Joe Biden .
This vaccine "has shown in clinical trials that it was effective" and cases of thrombosis "have nothing to do with its effectiveness," he insisted.
Today, the FDA and CDC recommended a pause in the use of the Johnson & Johnson vaccine.
Here's what you need to know: pic.twitter.com/QVtrEkqO8F
- President Biden (@POTUS) April 14, 2021
This product is 66% effective against the disease, 93% against the forms requiring hospitalization and 76% against the appearance of severe or critical symptoms, indicated the High Authority for Health (HAS) by validating it on the 12th. last march.
Are these the same side effects as for AstraZeneca?
Several cases of post-vaccination thrombosis have also been reported with AstraZeneca and, on paper, the two situations are very similar.
These two vaccines work on the same principle, that of the viral vector.
Another virus, in this case belonging to the adenovirus family, is modified and injected into the body with the aim of triggering the immune response to SARS-CoV-2.
AstraZeneca opted for a chimpanzee adenovirus, Johnson & Johnson for a human adenovirus.
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"The reported cases are probably a reaction of the immune system to an adenovirus, with a synthesis of antibodies called anti PF4 and which will be directed against blood platelets", describes the infectious disease specialist Benjamin Davido.
These platelets are theoretically used to thin the blood circulation.
"Anti PF4 are very prevalent in people vaccinated with AstraZeneca, and it is likely that it is the same mechanism with Janssen", adds immunologist Stéphane Paul.
Clinically, this mechanism is "similar to that of autoimmune thrombocytopenia induced by heparin", we also read in the conclusions of an article in the New England Journal of Medicine, published in early April.
Bad news !
đ
The CDC and FDA suspend the Janssen vaccine for cases of atypical thrombosis (1 case / million) in women <50 years
These cases do not currently exist with RNA vaccines.
Everything suggests that it is linked to the adenovirus vector, so what about sputnik?
https://t.co/3LQ6pmDCXu
- Mathieu Molimard (@MathieuMolimard) April 13, 2021
This disorder does not seem necessarily related to age, but as older people are more likely to develop a severe form of the disease, the benefit / risk ratio always outweighs them.
"If we observe the same phenomenon with two different vectors, there is every reason to believe that we will also observe it on other adenovirus vaccines", adds Stéphane Paul, referring in particular to the Russian Sputnik V and the Chinese Cansino .
What has France decided?
For the moment, nothing has changed.
The Janssen vaccine, the first 200,000 doses of which are expected this week, will be administered from next week to over 55s, government spokesman Gabriel Attal said on Wednesday.
At least that is what is planned "at this stage", according to the formula.
Asked Tuesday, the Ministry of Health also replied that this vaccine was anyway for the moment "marked" towards the 55 years and over.
This decision was taken "for consistency and for the sake of efficiency," the Minister of Health, Olivier VĂ©ran, told the JDD on Sunday.
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Without saying so, it may give the feeling that Janssen will remain, like AstraZeneca, off limits to younger people.
But the ministry assures that it is too early to establish it, pending the recommendations of the European Medicines Agency (EMA) (which has launched its own investigation).
It should communicate on this subject next week.
âAt the moment, there are not many people under 55 affected by vaccination.
In the short term, it would not be a problem to direct Janssen towards the elderly, âsuggests Benjamin Davido.
The infectious disease specialist pleads to announce now that this vaccine will remain banned for those under 55, "for the sake of consistency and to limit mistrust".
"You have to be pragmatic: if you end up with the same back and forth as with AstraZeneca, it's a disaster," he anticipates.
âYes, the same rules should be applied, there is no reason to do it differently.
I think the recommendations will fall very quickly, because we now know where to look for the cause of this kind of case, âadds StĂ©phane Paul.
Another expert does not wish to fuel a "deleterious cacophony", hoping for "a coordinated response at European level".
The opposite had happened for AstraZeneca, since the countries had announced in turn to suspend it in mid-March.
The authorized age groups then varied greatly from one State to another.
What could be the impact on the vaccination campaign?
It is difficult to say what the âdeployment delaysâ announced by the manufacturer mean.
âThe 200,000 doses planned were delivered this weekend.
At this stage, we have no comments to make on the announcement of Johnson & Johnson in relation to its impact on the vaccination campaign, âreplied the Directorate General of Health.
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By the end of June, the government plans to receive 8.1 million Janssen doses.
That is to say as many people potentially vaccinated, this product requiring only one injection.
By way of comparison, 11 million inhabitants have received at least one dose of vaccine in France, the vast majority (nearly 10 million) of which are at least 50 years old.
This represents a vaccination coverage of 37% of first-time vaccines in this age group (13% received two doses).
Suffice to say that there are still many potential candidates ... provided they remain volunteers.
In the immediate future, it would even be possible to suspend everything while the EMA and then the Haute Autorité de santé make their own recommendations.
"200,000 doses this week, that's not what will change the bottom line," says Stéphane Paul.
If we had had 10 million immediately usable, I would probably not have the same position â.
