A study by researchers from the Institut Pasteur seeks to assess the effectiveness of anti-Covid vaccines against variants of Covid-19.

Result: the Pfizer vaccine produces antibodies that are able to neutralize the Indian variant of the coronavirus, however with "slightly reduced efficiency" in the laboratory.

In people vaccinated with two doses of the Pfizer vaccine, the antibodies present in their blood serum are effective on the English variant, but slightly less effective against the Indian variant studied, according to this work published on the pre-publication site BioRxiv.

"The Pfizer vaccine is probably protective"

Despite "a slightly reduced efficacy, according to laboratory tests, the Pfizer vaccine is probably protective", reassures Olivier Schwartz, co-author of the study and director of the virus and immunity unit at the Institut Pasteur (Paris).

The researchers also tested the efficacy of the AstraZeneca vaccine on these variants, but only from the serum of people vaccinated with a single dose of the British vaccine, having "no access to samples of vaccinated with two doses" at the time of. the study, said Olivier Schwartz.

Since this vaccine only started to be used in the European Union in February and a 12-week period being recommended between the two doses, the second doses did not start to be injected until the end of April and in a number reduced number of people, because of its restriction to those over 55 and the disaffection with which it is the object in a part of the population.

A dose of AstraZeneca "ineffective" against the Indian variant

The results of the study, carried out with French university hospitals, show that a dose of the AstraZeneca vaccine, an effective vaccine against the English variant, "works very little against the Indian and South African variants".

A single dose of this vaccine therefore appears "little or not at all effective" against the Indian variant, underlines the researcher.

The Indian variant (B.1.617), detected in India in October 2020, has since diffused to many other countries, including the United Kingdom.

Its three main lineages or subgroups (B.1.617.1, B.1.617.2 and B.1.617.3) harbor certain mutations which can increase their potential for immune escape, i.e. their ability to reduce the effectiveness of antibodies generated by vaccines, antibodies acquired naturally or administered therapeutically.

The researchers specifically studied the B.1.617.2 virus, which seems to be more transmissible than the other two versions and which was recently detected in around ten countries.

“We show that this faster-propagating variant has acquired partial resistance to antibodies,” explains Olivier Schwartz.

For example, he continues, “the sera of patients who had Covid-19 and collected up to 12 months after symptoms as well as people who received the Pfizer vaccine remain neutralizing, but are three to six times less potent against (Indian variant) B.1.617.2 compared to B.1.1.7 ”(English variant).


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