the third vaccine dose, instructions for use

While the injections started on 1is September, Le Figaro answers your questions.

The High Authority for Health (HAS) has been recommending a booster dose of anti-Covid vaccine since August 24 to certain populations at risk. Injections started on 1is September, in town as in vaccination center. Who is eligible, and why? Instructions for use of the “third dose”.

The injection of a booster dose is recommended for populations most vulnerable to Covid-19. Among these are the categories who first benefited from the vaccination: residents of nursing homes and long-term care units, over 65 years old (over 80 years being priority), patients presenting a very high risk. severe form of Covid-19 due to a pathology listed by the Ministry of Health, or made more vulnerable by comorbidity (obesity, cancer, COPD, dementia, history of stroke, etc.). This also concerns people who have received the Janssen vaccine, as well as severely immunocompromised individuals (“Who have already received three doses and will receive a fourth”, specifies the opinion of the HAS).

  • Which vaccines require a booster?

The recall concerns all vaccines currently authorized in Europe against Covid: Comirnaty from Pfizer / BioNTech, Spikevax from Moderna, Vaxzevria from AstraZeneca and Janssen’s single-dose vaccine. Sometimes called the “third dose” (improperly for people who have already contracted Covid and therefore only received one dose of vaccine, or the one who received the Janssen vaccine which only involves one injection), the booster consists of one dose of RNA vaccine. It can be either Pfizer / BioNTech or Moderna, regardless of the serum initially received by the patient.

“The RNA vaccines from Pfizer or Moderna and the viral vector vaccines from AstraZeneca and Janssen all result in the production of the spike protein specific to Sars-CoV-2. The result is the same in terms of the production of antigens. On the other hand, RNA vaccines are more effective against the Delta variant, which explains why they are currently used as a booster ”, explains Prof. Elisabeth Bouvet, infectious disease specialist, president of the technical committee on vaccination at HAS.

Six months is the time after which we begin to observe a decrease in immunological markers in the blood. This is in addition to the lower efficacy of vaccines against the Delta variant which is prevalent at the moment.

Pr Elisabeth Bouvet, infectious disease specialist, president of the technical committee on vaccination at HAS

The HAS chose to authorize the booster six months after the end of the initial vaccination (one or two doses, depending on the case), and four weeks after the single injection of Janssen. “Six months is the time after which we start to observe a decrease in immunological markers in the blood. This is in addition to the lower efficacy of vaccines against the Delta variant which is predominant at the moment ”, explains Pr Bouvet.

  • What is the reason for calling back?

Providing a remote reminder of the initial vaccination is a “Classic scheme in vaccinology, notes Professor Jean-Daniel Lelièvre, head of the infectious diseases department at Henri-Mondor hospital, in Créteil. The protection thus induced should be more durable over time. We have a lot of data which tends to show that this recall is interesting, in particular for the most fragile people ”, who therefore need particularly strong protection. Scientists do not know at this point, however, whether an additional booster will ever be needed.

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