06/16/2021 7:20 PM
Clarín.com
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
4.9
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.
And
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
is
no
data
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.
But
"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
PB
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