A “break” for the Johnson & Johnson vaccine. The United States Medicines Agency (FDA) “is investigating six reported cases in the United States of people who developed rare and severe cases of blood clots after receiving the vaccine” Janssen de Johnson & Johnson, a- she said in a press release. And “as long as this procedure is in progress, we recommend a pause”, affirmed the FDA, specifying to act “for the sake of precaution”.

The U.S. Centers for Disease Control and Prevention (CDC) will meet on April 14 to assess these different cases. The US drug agency will then have to make a decision, based on their findings.

Delay in Europe

In the meantime, the American pharmaceutical group Johnson & Johnson said on April 13 that it had “made the decision to delay the deployment” of its vaccine in Europe.
France, in particular, was preparing to receive 200,000 doses the week of April 19, then 350,000 the following week.

Last week, the European Medicines Agency (EMA) also said it was investigating links between the “J&J” vaccine and cases of blood clots.

Read also: INFOGRAPHIC – We explain how the different types of vaccines work

Unusual and extremely rare thromboses

In the reported cases, the scientists observed a cerebral venous thrombosis, that is to say the obstruction by a clot of one or more cerebral venous sinuses, in association with low levels of platelets in the blood, underlines the institution.

The six people affected by these serious thromboembolic events are women aged 18 to 48 years, and their symptoms appeared six to 13 days after the injection.

More than 6.8 million doses of the Johnson & Johnson anti-Covid vaccine have already been administered in the United States and these types of serious side effects are currently “extremely rare”, the FDA said.

This announcement is reminiscent of the questions surrounding the AstraZeneca vaccine, for which the European regulator has asked that the risk of thrombosis be included in the side effects of this vaccine.

Read also: What we know about blood clots, a “very rare” side effect of the Astrazeneca vaccine

An effective single-dose vaccine

Johnson & Johnson’s single-dose vaccine was urgently authorized in the United States at the end of February, after two-dose vaccines from Pfizer / BioNTech and Moderna.

It has been shown to be 66% effective in preventing moderate to severe forms of Covid-19, according to clinical trials carried out on approximately 40,000 people aged 18 or over in several countries around the world.

A “viral vector”, the vaccine of “J&J” uses as a carrier another low virulent virus, transformed to add genetic instructions from a part of the virus responsible for Covid-19. Once in the cells, a typical SARS-CoV-2 protein is produced, educating the immune system to recognize it.