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Pfizer Covid-19 vaccine less effective against Indian B.1.617 strain, French study finds

The Pfizer vaccine is slightly less effective but appears to still protect against the more transmissible strain of the virus prevalent in India that causes Covid-19, according to a study by France’s Pasteur Institute.

“Despite slightly diminished efficacy, the Pfizer vaccine probably protects” against the variant found in India, according to laboratory test results, said Olivier Schwartz, the institute’s director and co-author of the study that was published on the BioRxiv website ahead of peer review.

The study sampled 28 healthcare workers in the city of Orleans. Sixteen of them had received two doses of the Pfizer vaccine, while 12 had received one dose of the AstraZeneca vaccine.




People who had received two doses of Pfizer saw a three-fold reduction in their antibodies against the variant, B.1.617, according to the study, but were still protected.

“The situation was different with the AstraZeneca vaccine, which induced particularly low levels of antibodies neutralising” the B.1.617 variant, the study said.

Patients who had had Covid-19 within the past year and people vaccinated with two doses of Pfizer retained enough antibodies to be protected against the variant prevalent in India, but three to six times less antibodies than against the UK variant, Schwartz said.



The study shows that “this variant.. has acquired partial resistance to antibodies,” Schwartz said.

Since first emerging in late 2019 in China, the SARS-CoV-2 virus that causes Covid-19 has developed several variants, usually named for the places where it first appeared including the so-called South Africa and UK strains.

The variant first detected in India appears to be much more transmissible than earlier variations. It has now been officially recorded in 53 territories, according to a World Health Organization report.