• On Facebook as on Twitter, a short sequence broadcast on LCI is enjoying great visibility these days.

  • We see a scientist from the Pasteur Institute affirming on the plateau: "We know that [the fact] of vaccinating more and more people will probably give rise to other variants resistant to immune responses".

  • Many opponents of vaccination thus rely on this sequence to prove the alleged dangerousness of vaccines ... even if it means indulging in an erroneous interpretation of admittedly clumsy remarks.

Would the fact of massively vaccinating the population against Covid-19 have the perverse effect of giving rise to more variants of the virus, and therefore increasing the danger of the disease?

This thesis, long supported by some opponents of vaccination, has just been confirmed by a researcher, according to a short video widely relayed these days on social networks.

We see Frédéric Tangy, director of the vaccine innovation laboratory of the Institut Pasteur, affirming on the LCI platform: "We know that [the fact] of vaccinating more and more people is probably going to give rise to other variants. resistant to immune responses.


A researcher from the Institut Pasteur finally comes out of his silence "We know that vaccinating more and more people will probably give rise to other variants resistant to the immune response"

So mass vaccination in the midst of an epidemic is dangerouspic.twitter.com / bqbefByQUt

- Carėne Tardy (@ Carene1984) September 8, 2021

“A researcher from the Institut Pasteur is finally coming out of his silence […].

So mass vaccination in the midst of an epidemic is dangerous ”, thus deduced - a little hastily - one Internet user, among the many others who relayed the sequence… which actually dates from the beginning of the year 2021.


The excerpt in question was indeed broadcast on February 4 on LCI, as we can see in the replay of this interview, still available on Facebook.

After having made these remarks (at 4:15), Frédéric Tangy nevertheless clarified his thoughts a few minutes later, emphasizing the interest of the vaccine strategy (at 5:45) in response to a question on the possible failure of vaccines by the variants: “It's a speed race with the virus.

If the variants are dragging a bit, we have time to adapt, to redo a vaccine composition for the next variant, but we can be out of gear.


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, Etienne Simon-Lorière, head of the evolutionary genomic unit of RNA viruses at the Institut Pasteur, regrets the "somewhat clumsy formulation, partly true and partly false" of his colleague and a "shortcut which can easily be misinterpreted ”.

"Vaccination against Covid-19 is very useful"

“A variant is born when the virus replicates in a person and does something stupid. Instead of putting a letter [in his genetic code], he puts another. This is very common. Most of the time this has no effect, or even the resulting virus works less well. But in certain cases, this can generate a variant which could have epidemiological success, ”explains Etienne Simon-Lorière.

“The more the virus circulates, the more likely it is to make mistakes and therefore to cause variants to emerge.

From this point of view, vaccination against [the] Covid-19 is very useful, because even if it is not perfect, it reduces the chances of infections.

And in people who become infected despite vaccination, this infection is generally shorter, with a lower viral load, so there is less chance of transmission and errors on the side of the virus, ”continues the specialist.

A variant that escapes the immune response?

A scenario "considered" but "not at all guaranteed"

For the head of the evolutionary genomic unit of RNA viruses at the Institut Pasteur, where the words of Frédéric Tangy are "not completely false, it is that in the future, when a large part of the population will be "immune" by exposure to the virus or through vaccination and that the virus will continue to circulate ", the latter will" be confronted with those people having an immune response.


“If a variant that appeared by chance is different enough, it is possible that it will have epidemiological success because it could at least partially escape the immune response, while other viruses are slowed down or blocked.

This is one of the scenarios considered for SARS-CoV-2, but which is not at all guaranteed, ”explains the specialist.

Etienne Simon-Lorière thus cites for comparison two different scenarios, illustrating the possible scenarios around Covid-19: seasonal flu as opposed to yellow fever or measles. Where the former manages to drift and escape immune responses (whether natural or related to vaccination) through a gradual build-up of mutations over the years, measles and yellow fever have "never been able to." to change enough to escape the vaccine ”, which explains why“ these epidemics affect unvaccinated people. "

"We do not know at all how things will turn out with SARS-CoV-2, hence a great deal of caution," warns the researcher, while stressing that "it is completely false to say that mass vaccination is very dangerous: on the contrary, it makes it possible to protect the population by limiting the risks of severe forms and of hospitalization […] and in addition it makes it possible to reduce the viral load and circulation of the virus, therefore the chances of revealing new variants problematic.



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