Will it be necessary to be vaccinated every six months against the coronavirus?

• From December 1, those over 50 will be able to booster the vaccine against Covid-19, provided they are at least six months after the second dose.

• With this close timing, some are wondering: is this a sign that all French people will have to do a booster dose, as is the case in the United States and Israel?

  Will it be necessary to repeat this operation every six months?

• The two researchers specializing in immunology interviewed by

  20 Minutes

  believe that despite the uncertainties, it would be surprising if these reminders were repeated so closely.

Barely a few months after receiving two injections of the Covid-19 vaccine, we will have to go back.

In any case for those over 50.

From December 1, they are encouraged to receive a booster if it has been more than six months since they received the second dose (or the single dose).

The starting signal for a vaccination against the coronavirus every six months for all?

Immunity wanes after six months

"It is an argument of antivax," regrets Eric Billy, researcher in immuno-oncology in Strasbourg. Who insists: there are many unanswered questions. “We cannot say today that we should not do a third dose for the entire population. But conversely, we can not say either that a fourth dose will be needed in six months. "

What we do know, on the other hand, is that "studies, particularly from Israel, show that after six months, immunity drops below a threshold that is considered not very protective" , insists the researcher, member of the collective Du Côté de la Science.

This is why insisting on the importance of giving a booster dose for all the elderly, immunocompromised or with co-morbidities, makes sense today.

On the other hand, "there is no evidence that administering a third dose in the general population is beneficial", qualifies the specialist.

A third dose that strongly boosts immunity

This recall campaign does not therefore sign, in view of current information, the start of a long tunnel of regular vaccinations for all. First of all because the immunity seems strongly reinforced by this third dose (it is not for nothing that it is called "dose booster" ...)

By popularizing: our immune system is divided into two parts. "B lymphocytes produce antibodies immediately, but there are also" memory "lymphocytes, which serve as a reserve for later in the bone marrow", explains Sandrine Sarrazin, researcher at Inserm at the immunology center of Marseille-Luminy. What we do not know at the moment is how many “memory B lymphocytes” are produced by this third dose. “But studies show that the second dose allows the production of 'memory B cells' in the bone marrow. And when we know how vaccination works, we can easily assume that this third dose again stimulates this long-term immunity. "

Especially since "the real data show that the third dose multiplies the level of antibodies in the blood by 5 to 15 times," adds Eric Billy.

This is much more than with the second dose.

So even if the immunity wanes over time, if ever it was necessary to do a new booster, it would not be six months after the third dose, but at least a year.

And this new recall would certainly only concern those who are eligible today.

"

"There is no reason to believe that we subscribe to a regular vaccination every six months"

Context may change

Sandrine Sarrazin adds that the global health situation has time to change in the coming months. “Depending on the context, we will not have the same protection strategy. This reminder comes in a particular context: in the midst of a pandemic, the virus circulates a lot. “Especially since France has entered a fifth wave a few weeks ago. "We arrive in the winter season, where it is more complicated to be outdoors and to ventilate for a long time," adds Eric Billy. We therefore need to raise the level of antibodies in these people who, if they encounter the virus, risk being hospitalized or even dying. The Delta variant being more virulent than Alpha, which was the majority last winter, it is advisable for this population to be well protected. "

“There is no reason to think that we subscribe to a regular vaccination every six months, continues Sandrine Sarrazin. If the virus stops circulating, we will have this memory immunity that protects us in the long term. Moreover, for other diseases, we do not need reminders so close. "To protect yourself against diphtheria-tetanus-poliomyelitis, for example, you have to have DTP boosters, but every twenty years ...

Why, then, do you have to get the flu shot every year?

“We often make the comparison with the flu, but we are in two different situations, corrects Sandrine Sarrazin.

This is not a booster, but a new vaccination, because it is not the same influenza virus.

For now, the third dose against the coronavirus is a booster.

»With exactly the same product as for the first vaccination.

The vaccination schedule being defined

Moreover, with this recent virus and full of surprises, scientists do not have enough perspective to be certain of the most protective vaccination schedule against Covid-19. “This is the first time that we have used RNA vaccines,” recalls Eric Billy. We were based on two doses, but it is possible that the protocol evolves with knowledge and mutations of the virus. Ultimately, it could be three doses. Changing a vaccination schedule is common, and many vaccinations today require three doses. "

In the future, we could therefore refine the vaccination schedule according to the patient profile.

Eric Billy believes that it would be interesting to launch a study on 30,000 people in France, who would be tested for antibodies one month and then four months after vaccination.

The goal ?

“Find out more about the drop in immunity depending on age and predisposition,” he explains.

Because today, we proceed in a systematic way: you are 50 years old, your immune system is no longer at the top, it is necessary that your circulating antibody level be brought up to you.

We are acting a bit blindly.

"

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