“Being vaccinated does not prevent you from having the Covid”: true or false?

What is the point of getting vaccinated, since it is not always enough to repel the virus? The argument is regularly put forward by opponents of vaccination. It’s true: being vaccinated against Covid is not an absolute guarantee against the disease. But the same goes for all vaccines. “No vaccine protects 100% “, Thus recalls the High Authority of Health (HAS).

The level of protection conferred by those used against Covid is, however, very high. According to a summary published in June 2021 by the authority, two doses of Pfizer or Moderna reduce the number of symptomatic cases by 90%. “Such efficiency is a chance, underlines Morgane Bomstel, research director at CNRS. In comparison, the smallpox vaccine is 72% effective. However, it has made it possible to eradicate the disease thanks to an active global vaccination policy. “

Fewer serious forms

Vaccines against Covid considerably reduce the risks of severe forms and therefore of hospitalizations. In the United States, 99% of deaths from Covid-19 are unvaccinated, according to the Center for Disease Control (CDC).

→ READ. Covid-19: the unvaccinated represent the “vast majority” of contaminations

In France, a study conducted among people over 75 by the scientific interest group Epi-Phare found that the risk of developing a severe form decreased by 87% as early as seven days after the second injection. “This means that they are nine times less likely to be hospitalized for Covid-19 than unvaccinated people over 75,” summarizes the study. “In France as in Europe, the vast majority of people hospitalized, especially in intensive care, have not been vaccinated”, also reports Professor Vassili Soumelis, immunologist at the Saint-Louis Research Institute.

Reduced risk of transmission

However, not having symptoms does not prevent being a carrier of the virus and at the same time, spreading it around you. “We must differentiate two things: on one side the infection, on the other, asymptomatic carriage, specifies Vassili Soumelis. If the vaccination has been successful, the person will not get sick, but it is not possible to be sure that they will not be a transient carrier of the virus after coming into contact with an infected individual. It’s very rare, but it happens, that’s why you have to be careful, without falling into paranoia ”, he puts into perspective.

Especially since according to the data collected by the HAS, vaccines “Reduce the frequency of asymptomatic SARS-CoV-2 infections and therefore the risk of transmission by vaccinated people: in the order of 80 to 90% for messenger RNA vaccines after two doses; around 70% for Janssen. ” Even vaccinated, a person presenting symptoms suggestive of Covid will tend to be more vigilant.

The need to receive a full vaccination

There remains the unknown of the Delta variant, more contagious and now the majority in France. According to the study published on July 8 by the Institut Pasteur in the journal Nature, the mutant would not change the equation much, even if the efficacy of the Pfizer and AstraZeneca vaccines appears “Slightly lower than against Alpha”.

→ DEBATE. Covid-19, do we need a third dose of vaccine for everyone?

On the other hand, the serum would become inactive or very little active ” for people who have received only one dose. Of these, only 10% had neutralizing antibodies in their blood, compared to 95% for those who received two doses. Hence the need, hammered by the authorities, to receive a complete vaccination.

80% of positive cases involved unvaccinated

The data recently collected by the DREES point in the same direction. Between June 28 and July 4, 80% of positive tests, i.e. the “Very large majority” of the cases, concerned unvaccinated people, calculates the statistics service of the Ministry of Health. Contamination in the vaccinated, they represented “only” 6% of cases. “By restricting itself to only patients who have declared themselves symptomatic, the proportion of people vaccinated completely among the positive tests taken is reduced to 4%”, specifies the study.

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Here again, the emergence of the Delta variant does not seem to significantly reduce the effectiveness of the vaccines. “During the same period, about 30 vaccinated patients were identified as carriers of a variant where the L452R mutation (carried mainly by the delta variant, NDLR) is detected, leading to a proportion of vaccinated people of 5.5%”, observes the Drees.


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