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Everything that is known in the world about coronavirus vaccines and how to deal with the Delta variant


A single dose of any vaccine is not very effective. But they become very resistant to the advance of Covid with two or three, depending on the vaccine.

06/16/2021 7:20 PM

  • Clarí

  • World

Updated 06/16/2021 7:20 PM

Faced with the Delta variant of the coronavirus, whose progress in the world is worrying,

vaccines are less effective

but protection against the disease remains important, as long as both doses are received.

Several laboratory studies show that the Delta variant (formerly called the "Indian variant")

appears to be more resistant to vaccines

than other mutations.

This is what is known as "immune escape".

According to one of these reports, carried out by the British authorities and published at the beginning of June in

The Lancet

, in people vaccinated with the two doses of Pfizer / BioNTech, the level of neutralizing antibodies

is almost six times lower

in the presence of the variant Delta than with the original strain, which was used to develop the vaccines.

In comparison, this reduction

is 2.6 times compared to the Alpha variant

("British"), and


times compared to the Beta variant ("South African").

Vaccination in Minas Gerais, Brazil, with Pfizer.

Reuters photo

Another study, conducted by the Pasteur Institute in France, concludes that neutralizing antibodies after receiving the vial of Pfizer / BioNTech

are three to six times less effective

against the Delta variant than against the Alpha.

Laboratory-recorded antibody levels are an essential indicator, but it is not sufficient to determine the efficacy of a vaccine.

The other facet of the immune response,

cellular immunity

, is not taken into account


Hence the importance of analyzing what happens in real life.


the results are rather reassuring.

The studies

According to data released Monday by UK authorities, vaccination with Pfizer / BioNTech and AstraZeneca

is just as effective

in preventing hospitalization for both the Delta and Alpha variants.

Two doses allow 96%

(for Pfizer / BioNTech) and 92% (for AstraZeneca)

to avoid

hospital admission due to the Delta variant, according to this study in 14,000 people.

Previous data from the British authorities gave

similar conclusions

for less severe forms of the disease.

Gabriela Moreira, 13, receives the vaccine from Pfizer-BioNTech in MInas Gerais, Brazil.

Reuters photo

Two weeks after the second dose, the Pfizer / BioNTech vaccine is

88% effective

against the symptomatic form of COVID-19 due to the Delta variant, versus 93% for the Alpha variant.

For its part, AstraZeneca shows an efficiency of 60% and 66% against these mutations.

The creators of the Russian vaccine Sputnik V claimed on Twitter Tuesday that their drug was

"more effective against the Delta variant"

than any other, but did not publish their data.

Studies converge on one point:

a single dose provides limited protection

against the Delta variant.

"After a single dose of Pfizer / BioNTech, 79% of people had a detectable antibody response against the original strain, but this dropped to 50% for the Alpha variant, 32% for the Delta variant and 25% for the Beta variant" concludes the laboratory study published in June in

The Lancet


According to the Pasteur Institute research, a single dose of AstraZeneca would be

"little or not at all effective"

against the Delta variant.

These trends are confirmed in real life: according to the British authorities, a single dose of either vaccine

is 33% effective in

preventing the symptomatic form of the disease caused by Delta (and 50% for the Alpha variant). ).

Complete vaccination

Among all licensed immunizers, only Janssen's is single-dose.

For now, there




on your protection against the Delta variant.

To stop the spread of this variant, 60% more transmissible than Alpha according to the British authorities, scientists insist on the importance of full vaccination,

with two doses.

Creating this

"block of vaccinated",

in the words of the president of the French Scientific Council Jean-François Delfraissy, has a second objective: to prevent other variants from emerging from the population that is partially or not protected at all.

The prospect that worries more

is the appearance of other mutations of the virus,

more resistant to vaccines.


"you don't have to base everything on vaccination,"

epidemiologist Antoine Flahault told AFP.

According to him, it is crucial to

"keep the virus circulation very low",

through the other control measures (barrier gestures, case detection, restriction measures ...), since the more the virus circulates, the more possibilities there are. to mutate and create other variants.

Source: AFP


Look also

Coronavirus cases fell 12% worldwide in the last week

Novavax Offers U.S. Fourth Strong COVID-19 Vaccine

Source: clarin

All news articles on 2021-06-20

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