Coronavirus: Understand everything about the (new) vaccine booster campaign – 20 Minutes

On Tuesday, only 3.4 million of the 7.7 million French eligible had their recall (the third dose) of the vaccine against
Covid-19. They should be much more numerous in the coming weeks. Emmanuel Macron has indeed modified the recall campaign … with the objective of boosting it. And thus slow down the epidemic resumption.

For the moment, only those over 65, people with co-morbidities and professionals caring for and supporting these patients (caregivers, medical transport, home help, medico-social professionals, etc.) can receive a booster dose ( the second, the third or even the fourth dose according to the profiles of the people). But from December 1, access will be extended to over 50s. On the constraint side this time, people over 65 who will not have had this booster after December 15 (when their second dose or single dose dates from six months and five weeks) will lose their health pass. 20 minutes takes stock in five questions.

Why this reminder?

During vaccination, our body produces two types of protection against the virus. “B lymphocytes produce antibodies right away, but there are also ‘memory’ lymphocytes which serve as a reserve for later in the bone marrow,” explains Sandrine Sarrazin, Inserm researcher at the Marseille-Luminy immunology center. This explains why the majority of vaccines, injected before a child’s first birthday, protect him for years.

“The booster is not mandatory for traditional vaccines,” admits the researcher. There is certainly the DTP, which requires a recall every twenty years, then every ten years after 65 years. “Not every six months, so … Why then these recalls against Covid-19 so early? “The context is different: on the one hand, we are in the midst of an epidemic, insists Sandrine Sarrazin. On the other hand, it is not yet known how long this immunity lasts. What we do know, however, is that it decreases over time. After six months,
according to some studies.

“For everyone, but it is correlated with age”, nuances the researcher. Basically, the older you are, the faster your immunity drops. Hence this prioritization of the recall campaign. “Studies of patients who participated in clinical trials and in real life in Israel [où les troisièmes doses ont commencé dès la fin juillet 2021, et ont été élargies aux plus de 12 ans fin août] show that the booster increases the level of antibodies in the blood tenfold, ”adds the researcher. With proven effectiveness: in mid-September, the rate of severe cases was around 4 per 100,000 inhabitants among “triple vaccinated”, against 35 per 100,000 for people who received one or two doses, and 150 per 100,000 for the unvaccinated, according to Israeli health authorities.

With which vaccine?

Whatever vaccine is injected during your first vaccination, you will necessarily receive Pfizer (Comirnaty). With a six-month delay between your last injection and this booster. Unless you have opted for the Jannsen vaccine, the waiting time between the first and single dose and this booster is reduced to four weeks.

But things could very well change. Indeed, according to the report of the High Authority of Health of November 8, Moderna seems to be more effective in preventing severe forms. On the other hand, the HAS specifies that for those under 30 (suffering from comorbidities, likely to have serious forms or caring for vulnerable people, caregivers, home helpers, etc.), the Pfizer vaccine should be preferred because the risk of having myocarditis after the injection (which remains very rare) is 5 times less for the latter compared to the Moderna vaccine.

Is the booster injection less dosed?

It depends on the vaccines. For Moderna, we go from 100 micrograms for the primary vaccination to 50 micrograms for the booster. Why ? “In their phase 3 clinical trial, patients received 100 micrograms of the vaccine developed by Moderna,” recalls Sandrine Sarrazin. The lab has since tested different doses and found that with 50 micrograms it was enough. »Useful to save doses: with the same quantity of product, we can vaccinate twice as many people. “Pfizer’s vaccine, on the other hand, was at 30 micrograms for the primary vaccination. They didn’t do a test to divide the dose. As there is a good reaction, there is no change during the third injection. “

Should we expect other side effects?

The National Medicines Safety Agency (ANSM) has set up specific monitoring of adverse effects reported after a booster dose. Result: since August 24, date of the launch of the recall campaign, 78 serious cases have been reported for the Pfizer vaccine. On the side of Moderna, there are 28 serious cases. For these two vaccines, “the undesirable effects reported are similar to those of the primary vaccination, and no specific signal has been identified concerning the booster doses and the 3rd doses. », Specifies the ANSM in its press release. But the booster of Moderna, less dosed than the primary vaccination, could it limit the side effects? “It is not correlated like that, reactions change from one person to another, nuance Sandrine Sarrazin. What is certain is that we will not have side effects that are more important or different from those caused by the first injections. “

Can we combine influenza vaccine and booster dose against Covid-19?

Yes, this double protection is even recommended by the health authorities, since the first victims of Covid-19 are the same as those of the flu. It is therefore already possible to receive these two vaccines on the same day, but at two injection sites. “The concomitant realization [de ces] vaccines “does not involve” any danger “and can allow” to avoid any delay in the administration of one or the other of these injections “, underlines the HAS.

Are these people more likely to be HS with both arms sore? “There is no more risk of side effects,” says Sandrine Sarrazin. Remember that our children sometimes receive pentavalent vaccines (protecting against five different diseases). What if you’ve already had your booster or flu shot? There is no time limit between these two injections.