Doses of Johnson & Johnson coronavirus vaccine in Los Angeles, March 25, 2021. – Frederic J. BROWN / AFP
- US health authorities on Tuesday recommended “a pause” in the use of the Johnson & Johnson Covid-19 vaccine after six cases of cerebral venous thrombosis in people vaccinated in the United States.
- The US Medicines Agency (FDA) has opened an investigation into a possible link between the vaccine and cases of blood clots. In the process, the American pharmaceutical group indicated that it had “taken the decision to delay the deployment” of its vaccine in Europe.
- But why this decision? And with what consequences in Europe? We take stock.
A month and a half after being approved in the United States, the American health authorities on Tuesday recommended “a pause” in the use of the anti-Covid vaccine produced by Johnson & Johnson to investigate serious cases of blood clots in several people. A few hours later, the American pharmaceutical group indicated that it had “taken the decision to delay the deployment” of its vaccine in Europe, pending the conclusions of the health authorities.
Why is the vaccine suspended? How many cases of serious side effects have been identified? What is the impact on deployment in Europe? 20 minutes provides an update on the temporary suspension of this vaccine.
Why was the vaccine suspended?
Use of the vaccine was put on hold after “six reported cases in the United States of people who developed rare and severe cases of blood clots after receiving the vaccine,” the United States Medicines Agency (FDA) said. who opened an investigation on Tuesday. “One case has turned out to be fatal and one patient is in critical condition,” said an official. In total, more than 6.8 million doses have been injected in the United States.
In the reported cases, scientists observed a very unusual cerebral venous thrombosis, i.e. clot obstruction of one or more cerebral venous sinuses, the institution pointed out. These thromboses are accompanied by a drop in the level of blood platelets, cells that help blood to clot and can cause hemorrhages in addition to blood clots, warned US health officials, who advocate alternative treatment.
How can we explain these thromboses?
Although nothing is proven yet, it is increasingly likely that these blood problems are related to the technique on which this vaccine is based. Like that of AstraZeneca, the Johnson & Johnson vaccine is a so-called “viral vector” vaccine: we take another virus as a carrier, which we modify so that it carries genetic information in the body to fight the Covid .
Both vaccines use a very common type of virus called adenovirus as a carrier. AstraZeneca opted for a chimpanzee adenovirus, Johnson & Johnson for a human adenovirus. The fact that similar problems were observed with these sera could suggest “that it is linked to the adenovirus vector,” said Mathieu Molimard, French pharmacology specialist, on Twitter. Indeed, “these cases do not exist to date with RNA vaccines”, those of Pfizer / BioNTech and Moderna, which use another technique, messenger RNA.
What are the risk factors?
The six people affected by these serious thromboembolic events are women aged 18 to 48 years, whose symptoms appeared 6 to 13 days after the injection. Regarding AstraZeneca, most of the cases observed also concern “women under 60”, according to the European Medicines Agency (EMA). But it is too early to draw a conclusion. “According to the information currently available, we have not identified a specific risk factor,” commented the EMA about AstraZeneca.
When can the Johnson & Johnson vaccine be reauthorized?
The American Centers for Disease Control and Prevention (CDC), the country’s federal public health agency, are due to meet on Wednesday to assess these different cases. The US drug agency will then review their findings. “As long as this procedure is in progress, we recommend a pause”, affirmed the FDA, specifying to act “for the sake of precaution”.
Why has the vaccine rollout in Europe been delayed?
The American pharmaceutical group Johnson & Johnson said on Tuesday that it had “made the decision to delay the deployment” of its vaccine in Europe pending the conclusions of the American health authorities. Johnson & Johnson “is investigating these cases with European health authorities,” the group said in a message, without giving further details on the length of the postponement. For its part, the European Medicines Agency (EMA) announced last Friday to examine a possible link between the Johnson & Johnson vaccine and cases of blood clots.
What consequences for the use of the vaccine in Europe?
The European Union, which authorized the Johnson & Johnson vaccine on March 11, had pre-ordered 200 million doses, with the possibility of doubling the order. France, the first European country to deploy it on its territory, received “200,000 doses” on April 12, “one week in advance”, the Minister of Health had indicated.
If the deployment of additional doses is delayed in Europe, the European and French health authorities have not formally suspended the use of this vaccine for the moment. However, no injection has been identified at this stage in France, according to data published daily by Public Health France.
Note that the Johnson & Johnson vaccine can be stored for three months at standard refrigerator temperatures.