This is very good news published by the prestigious journal New England Journal of Medicine July 21: the anti-covid vaccines Pfizer and AstraZeneca remain very effective against the Delta variant, currently the majority in France.

Fear of an immune escape

The study, coordinated by the British public health agency, started from a fear: that the mutations of the Delta variant offer the virus an immune escape. In other words, that this variant is so different that it manages to escape the recognition of an immune organism by vaccination.

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88% efficiency for Pfizer

The researchers therefore studied the vaccination status of people infected with the Dellta variant of the coronavirus (positive PCR test) and uninfected (negative PCR test). Result: they observed that the vaccines were almost as effective against infection by the Delta variant as by the Alpha variant (initially called the British variant).

Thus, the Pfizer vaccine, 93.7% effective against an Alpha variant infection, is 88% effective against a Delta variant infection.

And the AstraZeneca vaccine, 74.5% effective against an Alpha variant infection, is 67% effective against the Delta variant.

One dose is not enough

Provided of course to have received the two doses. And this is precisely where it can get stuck: while the first dose already gave the vaccinated person a fairly good protection against the Alpha variant, this is not the case for the Delta variant.

In fact, a dose of Pfizer vaccine only reduced the risk of Delta infection by 30.7%, when it reduced it by almost 50% against the Alpha variant.

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Faced with the Delta variant, it is therefore necessary to be extra vigilant about the “vaccinee syndrome”, this slack behavior due to a false feeling of protection after the injection of the first dose of vaccine.

As of July 22, the Delta variant represented 79% of new cases of coronavirus when 46% of French adults had received two doses of vaccination and 56% at least one dose of anti-covid vaccine.