People over 65 who received the second dose more than six months ago are eligible for a third injection. This six-month deadline was established by the General Directorate of Health (DGS), which followed the opinion of the Haute Autorité de Santé of 23 August 2021.
→ FILE. 3rd dose: answers to your questions about the vaccine booster
This period takes into account the results of studies indicating “A drop in the efficacy over time of all vaccines against Covid-19, in particular against the Delta variant”, according to the DGS. Note that this period is shortened to three months for people with severe immunosuppression. Another exception: people who have received a dose of Janssen during the primary vaccination, for whom the time limit is reduced to one month.
It is in particular a study by the Institut Pasteur, published on July 8, 2021, which demonstrated the lower resistance of antibodies to the Delta variant, explains Morgane Bomsel, virologist at the CNRS and at the Institut Cochin. ” The cells which have been educated to develop antibodies against the virus with the first injections of the vaccine, produce less after a certain time ”, explains the researcher. With the injection of a 3rd dose, these antibodies are stimulated again, they are more numerous and more able to recognize the virus in the event of infection.
→ INVESTIGATION. 3rd dose: “How to make an appointment for a new injection against Covid?” “
The decrease in the ability to resist the virus varies from person to person, “But what we know is that it does not drop for six months”, adds Morgane Bomsel. Getting vaccinated before this time is not dangerous, but is unnecessary.
→ ASK YOUR QUESTION. Covid-19 vaccine: ask your questions about the third dose