Third dose: unlike the first two, the “booster shot” effective from 48 hours – LCI

Near “5 million French people have recalled” to date, welcomed this Thursday the spokesman of the government, Gabriel Attal on LCI. But the battle is far from won when 7.7 million people are eligible. However, at the beginnings of a “fifth wave of the epidemic, with a number of contaminations, an incidence which is progressing very rapidly, of the order of 40 to 50% per week for two weeks now”, as he said in a post-Council of Ministers press briefing, the stakes are high to avoid new hospital tensions in the weeks to come.

It is undoubtedly all the more so since this third injection, also called “booster shot” and intended to reinforce the immune protection conferred by the first two doses, acts almost instantaneously.

“We must continue to vaccinate”, said Wednesday on LCI the president of the scientific council Jean-François Delfraissy insisting on the fact that the vaccine “does the job on protection against severe and severe forms, and that’s what is important “, with the same observation for the third dose in the elderly. “When you get a booster, it is effective 48 hours later. There is an immediate boost in immunity.”

From a scientific point of view, a consensus exists around this booster dose for people called “immunocompromised”, that is to say with a weakened immune system. Studies have indeed shown that despite vaccination, their body does not produce enough antibodies (main criterion for evaluating the effectiveness of vaccines). Even if we have less data, the reasoning is the same for the elderly, whose immune system is made less effective by aging.

For the moment, residents of nursing homes, people over 65, people at very high risk of severe disease (presenting comorbidities, immunosuppressed, etc.) are eligible for this booster dose. Since the beginning of October, health professionals, firefighters and relatives of immunocompromised people have also been concerned. From December, this will also be the case for people over 50. The latter should be administered 6 months after the last vaccine injection.

If the third, called “booster”, therefore further strengthens the immune response, it is the first dose which “activates” our immune system while the second acts as a reminder, a “consolidation”. However, as a reminder, concerning these first two injections, the first protective effects do not occur for a week after the studies.

In detail, concerning the Pfizer vaccine, the first dose does not really begin to protect the vaccinee until two weeks after the injection, when the second, according to a study carried out in Israel, and published in the journal The Lancet at the beginning of May reveals “highly efficient” seven days later. With regard to the Moderna vaccine, the protection “begins 14 days after the first dose”, according to the World Health Organization, while the effectiveness of the vaccine is complete two weeks after the injection of the second dose, when a person is considered “fully vaccinated” explains the American Center for Disease Control (CDC).

As of the publication of preliminary data on the effects of a third dose of Pfizer, a jump in the level of anti-Covid antibodies had been demonstrated, by a factor of five to ten in fully vaccinated adults, detailed at l then Mikael Dolsten, head of research and development at Pfizer with the American news agency Associated Press. This summer, a first Israeli study finding the beneficial effects on the elderly, had initially concluded to “an 11.4-fold decrease in the relative risk of confirmed infection, and a greater than 10-fold decrease in the relative risk of severe disease”, within “twelve days or more after the booster dose”.

According to Pr Delfraissy “we will very probably have to go towards a third dose” vaccine “in the general population”. Asked about this on Europe 1, the “Mr. vaccination” of the government, Professor Alain Fischer, said that “without doubt, the moment of recall will come, each thing in its time”, the third dose for the entire population being “very probable”. Believing that “the problem is not really an age problem” corn “that after six to seven months, the antibodies drop”, infectious disease specialist Benjamin Davido, for his part, considered last week on CNews that “this boost of immunity would clearly allow the stopping of contaminations between vaccinated persons”.