Will a third dose be required for all vaccinated? This is what Pfizer / BioNTech recommends to deal with the Delta variant. The two companies have already announced that they would ask “in the coming weeks“the authorization for a third dose of its vaccine in Europe and the United States.

Six to 12 months after the second dose

This could be given six months to a year after the second dose, to boost the levels of neutralizing antibodies against the virus in the blood.

Because “although the protection against severe cases of the disease remains high for six months, a decline in its efficacy against symptomatic cases over time and the emergence of variants is expected“says Pfizer / BioNTech in a statement.

Read also: Infection or vaccination, the same immunity?

A 3rd dose for the first vaccinated

This booster dose is already administered to the most fragile people, such as immunocompromised people or people on immunosuppressive treatment to strengthen their immune protection.

A precaution which should soon be extended “to the most vulnerable, vaccinated first“, Prime Minister Jean Castex declared on July 8.

“Both because they are vulnerable and because this vaccination took place early, we will need a third dose because the immune defenses are weakening.“he clarified.

Two insufficient doses against the Delta variant?

And this is also what the Institut Pasteur breathes in a study published on July 8 in the journal Nature. According to the scientists signing this study, the more contagious Delta variant is also more resistant to anti-covid vaccines than other strains of coronavirus.

Higher antibody levels are thus necessary to neutralize this variant: it would take four times more than for the other variants. And to reach these levels and especially to maintain them over time, three doses of vaccine may be required.

What is certain, for the researchers at the Institut Pasteur, is in any case that a single dose of vaccine is not sufficient to protect against the Delta variant because it does not trigger a strong enough immune response.

A chance for the Sanofi vaccine?

But which vaccine to use for the third dose? The same as the first two doses or not, it doesn’t matter. Vaccine efficacy would even be enhanced if vaccines differ between the first, second or third doses, scientific studies suggest.

This leaves hope for the late Franco-British vaccine from Sanofi / GSK, which could be available in December 2021, according to the president of the French laboratory.