• After receiving their first injection of the coronavirus vaccine, some people think they are directly immune.

  • This phenomenon, called "vaccinee syndrome", is dangerous: it takes 10 to 12 days for the first dose to produce effects.

    Effects which are moreover insufficient.

    Because it is the second injection that guarantees maximum protection.

  • How to explain this phenomenon ?

Once their first dose of vaccine against the coronavirus has been received, would the French tend to relax too much?

The phenomenon, not quantified, begins in any case to talk about him and to worry, to the point that he has already inherited a name: the "syndrome of the vaccinated".

These would be people who think they are protected from the first injection and then live without respecting barrier gestures.

An attitude as casual as it is dangerous.

An insufficient first dose

Certainly, the first dose offers a strengthening of the immune system against the coronavirus. But the latter does not arrive until ten to twelve days on average after the bite (this time interval depends on the type of person and his age group). Eric Billy, researcher in immuno-oncology and vaccine specialist for On the side of science, informs: “The first dose arrives in an immune space normally still virgin of any Covid-19. It takes time for the machine to start up. "

While waiting for the end of these ten to twelve days, the person therefore has an immune system that is still completely neutral in the face of the coronavirus, and is not at all protected.

“You can't get vaccinated on Tuesday and go to the evening on Friday thinking you're immune,” recalls the researcher.

An interval that explains in particular the high-profile cases of individuals who received a first dose and still had serious forms of coronavirus.

And yet, the protection of the first dose is only partial, and far from guaranteeing total protection as a person can have fifteen days after his second injection.

Yes, an effect is observed and there is a decrease in the symptomatic forms of the coronavirus on D + 10/12.

But be careful not to overestimate this effect.

In the United Kingdom, for example, the vaccination strategy has been based on the first doses, even if it means postponing the second injections as much as possible. It has shown very positive effects on the epidemic. Not only was it coupled with long and strict confinement, but it also took place within an already highly infected population. A study carried out in Scotland showed that more than 50% of those 80 and over already had antibodies against the coronavirus, so had already been infected. However, for people who have already had Covid-19, the first dose acts as a second dose, a booster. This could have led to a slight overestimation of the immunity acquired by the first dose.

It should also be remembered that faced with the rise of the Indian variant, the United Kingdom is currently hesitating to slow down its deconfinement, the time to vaccinate more patients via a second dose, in order to offer them better immunity.

A real trend?

How then to explain this phenomenon of "vaccinee syndrome"?

“There may have been too many highlights of the number of first-time vaccines in France, as if that was enough or an objective in itself.

The number of people fully vaccinated is put in the background, which may mean that the second dose is not that important or decisive ”, theorizes Michaël Rochoy, researcher in epidemiology and vaccinator.

However, the two experts assure him, the phenomenon remains very marginal. "We talk about it a lot because a person who has just received their first dose and who catches the coronavirus is tearing their hair out," reveals Michaël Rochoy. But in reality, the overwhelming majority are aware. Eric Billy indicates that each doctor who vaccinates in the first dose informs of the importance of being careful and of waiting for the famous two weeks after the second dose before slacking off. "And again, since we are still a possible transmitter of the virus, we should not fully relax with people who are also fully vaccinated," he says.

For Michaël Rochoy, the proof that the phenomenon remains minimal is in the figures of the coronavirus.

The current drop in all health indicators in France, "it is the demonstration that even first-time vaccinated, people continue to pay attention", he rejoices.

Good news to keep busy while waiting for the second dose.

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