Is Eric Zemmour in favor of the principle of the sanitary pass? Guest of the program “Elysée 2022”, Thursday December 9 on France 2, the far-right candidate for the presidential election declared to have forged a conviction: “I understood that in fact, it was of no use.” Why ? “For a simple reason: the vaccine [n’empêche] not transmission and contagion, and [n’empêche] in truth that the serious cases… From that moment, one can be with someone who is vaccinated or not, that does not change anything, one can catch it anyway, so the health pass is useless. “
At a time when France is generalizing the campaign to recall the vaccination against Covid-19 to all adults, the former journalist is not the only one to make this type of statement. Before him, the deputy for rebellious France François Ruffin assured at the end of October, to the National Assembly, than “despite the vaccination, [le virus] continued to be transmitted “. Is this argument admissible? Franceinfo recaps.
Let’s start with a reminder: the vaccines currently administered around the world were designed to neutralize the original strain of Covid-19, identified in Wuhan, China, at the end of 2019. After an injection, the immune system begins to produce antibodies which target the spicule (or spike protein in English), which plays a key entry role for Sars-CoV-2. If this is correctly neutralized, the virus is not able to infect the body. Logical consequence: a person who has not contracted Covid-19 cannot transmit it.
While they have never guaranteed 100% efficacy against infection, the vaccines showed very encouraging results in this area at the start of the vaccination campaign. “Messenger RNA vaccines, which are the most effective today, provide 90% protection after the second dose against symptomatic forms of the disease, and 80% against asymptomatic forms”, explained to franceinfo last April Anne-Claude Crémieux, professor of infectious diseases at Saint-Louis hospital, in Paris.
Despite a lower risk once the first two-dose vaccination schedule has ended, it is therefore still possible to contract the disease. But it is for all that inaccurate to assert, as Eric Zemmour does, that being around a person vaccinated or not “do not change anything” the likelihood of being infected in turn. “We estimate that the contagiousness of an infected but vaccinated person is reduced by 40% compared to an unvaccinated person”, supported at the end of October Parisian Samuel Alizon, evolutionary biologist at the CNRS in Montpellier. The Institut Pasteur, for its part, estimates that infected vaccines have 50% less risk of transmitting the virus than unvaccinated people.
Over the months, however, the situation has changed. Almost nonexistent until June, the Delta variant has since swept over France, to the point of representing 99.4% of Sars-CoV-2 cases sequenced by laboratories during the week of November 22. However, the protection conferred by vaccines against this variant is less than against the strain “historical” identified in Wuhan, as announced by the World Health Organization.
In a study published on November 25 in The Lancet, the Institut Pasteur noted that a person vaccinated with two doses of Pfizer-BioNTech or Moderna vaccine who had never contracted Covid before was 67% protected against a symptomatic infection linked to the Delta variant, even if the protection against severe forms of the disease remain important. Other works published in this leading medical journal point in the same direction.
According to a new study published in The Lancet, the effectiveness of the vaccine #Pfizer against Delta variant infection would drop from 93% during the first month after full vaccination to only 53% four months later. # Covid19 https://t.co/PC5YKsXxUi
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– Nicolas Berrod (@nicolasberrod) October 5, 2021
At the same time, the level of neutralizing antibodies generated by a two-dose vaccination tends to decrease gradually over the months. This fall even becomes “significant” between five and eight months after the administration of the second dose, explains to franceinfo Sandrine Sarrazin, Inserm researcher at the Marseille-Luminy immunology center.
It is in the face of the combined threat of reduced vaccine efficacy linked to the Delta variant and a slow decline in this level of neutralizing antibodies that the French authorities have decided to generalize the injection of a third dose to the set of adults. The interest is established: by presenting once again to the immune system a pathogen with which it has already been confronted, the booster dose makes it possible to jump the level of antibodies to a level “ten to twelve times higher” to the one following the second injection, according to this researcher.
The consequences in terms of transmission of the virus are felt. Israeli study of over 300,000 patients published on November 30 (article in English) showed that the proportion of positive PCR tests presented by people who received a booster was 86% lower than that of simple “double vaccinated”. “A person vaccinated with a booster will acquire the virus less often, and when they are infected, their viral load will be lower: statistically, they will be less transmitting”, summarizes for franceinfo Olivier Schwartz, head of the virus and immunity unit at the Institut Pasteur.
“With the third dose, we will again be able to affirm that the vaccines protect against the transmission of the virus. The Delta variant and the gradual decline in immunity after the second dose had made us lose this advantage, but we should regain it thanks to to the reminder “, concludes Sandrine Sarrazin.