One study suggests “a slight increased risk of myocardial infarction” within two weeks of being injected with the Janssen vaccine. Consequently, the HAS advises to use this serum only in certain specific cases.
The High Authority for Health (HAS) recommended on February 21 the postponement of vaccination with the anti-Covid Janssen vaccine, “with the exception of people at risk of a severe form of the disease who have a contraindication to administration of an mRNA vaccine”.
As a reminder, the Janssen vaccine is the name of the serum from Johnson & Johnson and its Belgian subsidiary in the EU. Unlike the Moderna and Pfizer laboratory sera, it is not based on mRNA technology, but on the principle of the viral vector, like that of the AstraZeneca laboratory. Its main advantage is that it only requires a single dose, which speeds up immunization campaigns.
The HAS is based on a study whose results “suggest a slight increase in the risk of myocardial infarction in the two weeks following vaccination with the Janssen vaccine” in people under 75 years of age.
However, the results of the study are preliminary and have not yet been confirmed or invalidated by other studies. The European Medicines Agency must also look into the subject, according to the HAS. Pharmacovigilance data at the global level do not show an increased risk in this area at European or American level, even though more than 38 million doses of the Janssen vaccine have been administered.
However, the use of the Johnson & Johnson vaccine raised concerns in 2021. The Medicines Agency had thus noted last September “an overrepresentation of patients vaccinated by Janssen in intensive care”. In addition, two hospitals had at the same time reported an abnormally high number of patients vaccinated with Janssen among those hospitalized in intensive care. So many elements that had prompted the Medicines Agency to conduct “additional investigations”.