Are Covid-19 vaccines effective in combating the so-called “Indian” variant? The latest Institut Pasteur study on the issue is reassuring, at least for the messenger RNA vaccine from Pfizer-BioNTech. The latter produces antibodies capable of neutralizing the B.1.617.2 variant, with however a “Slightly reduced efficiency” in the laboratory, according to this study, published Friday, May 28 on the pre-publication site BioRxiv.
In people vaccinated with two doses of the Pfizer vaccine, the antibodies present in their blood serum are effective against the English variant, but slightly less effective against the Indian variant studied, according to the results of this work. 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).
Antibodies “three to six times less potent”
The B.1.617 variant, detected in India in October 2020, has since spread to many other countries, including the United Kingdom. Its three main lines 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 appears to be more transmissible than the other two lineages and which has recently been detected in around ten countries. “We show that this faster-spreading variant has acquired partial resistance to antibodies”, explique M. Schwartz.
For example, he continues, “The sera of patients having had a Covid-19 and collected up to twelve months after the symptoms as well as people who received the Pfizer vaccine remain neutralizing, but are three to six times less potent against B.1.617.2 [variant indien] compared to B.1.1.7 [variant anglais] ».
A single dose of AstraZeneca “little or not effective”
The researchers also tested the effectiveness of the AstraZeneca vaccine on these variants. The study is limited, however, to people vaccinated with a single dose of the British vaccine, since the researchers did not have 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 period of twelve weeks being recommended between the two doses, the second doses did not start to be injected until the end of April. The number of patients concerned has also been reduced due to the restriction of use of the vaccine to those over 55 years of age and the disaffection to which it is the object in part of the population.
The results of the study, carried out with French university hospitals, show that a dose of the AstraZeneca vaccine “Works very little against 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.
A recent study by health authorities in England, Public Health England (PHE), however, established that AstraZeneca serum was 60% effective against the Indian variant. “Two doses [du vaccin de Pfizer ou d’AstraZeneca] offer high levels of protection against symptomatic disease of variant B.1.617.2 “, concluded Mary Ramsay, head of PHE immunization.