Does one dose of Janssen protect enough? “A large number of cases of failure of the Janssen vaccine has been reported, with in particular serious forms (death, resuscitation) as well as an over-representation of patients vaccinated by Janssen in intensive care in two CHU”, in Marseille and Tours, notes l ‘ANSM in its periodic vaccine surveillance report.
Since April, around one million injections of this vaccine produced by the Johnson & Johnson laboratory and which only works with a single dose, have been carried out in France. Among all these people vaccinated with Janssen, 32 cases of Covid-19 infection have so far been reported, a rate of 3.78 per 100,000. Of these 32 cases, 29 were serious and 4 deaths were recorded. These seriously affected patients were between 73 and 87 years old and presented “mostly serious risk comorbidities”, according to the ANSM. For the 17 cases of infection where the variant is known, it was each time the Delta variant.
In addition, two hospitals reported an unusually high number of patients vaccinated with Janssen among people hospitalized in intensive care despite vaccination. In Marseille, out of 7 patients who were fully vaccinated but still admitted to a sheave (that is to say seriously affected), 4 had been with Janssen. In Tours, this proportion was 3 out of 6.
All these elements justify “additional investigations” to check whether the failures are more important with Janssen than with the other vaccines available in France. On August 24, the French National Authority for Health (HAS) recommended that people vaccinated with Janssen receive a booster dose with an mRNA vaccine (Pfizer or Moderna) from four weeks after their vaccination.
Several real-life studies have indeed shown that the first dose of Pfizer or AstraZeneca vaccine provided insufficient protection against the Delta variant. No data on this point is available for Janssen, but the HAS had deemed it likely that this is also the case.