Covid-19 vaccines made by AstraZeneca and the Pfizer-BioNTech alliance remain broadly effective against Delta and Kappa variants of the coronavirus, which were first identified in India, according to a scientific study, underpinning a continued push to deliver the shots.

The study by Oxford University researchers, published in the journal Cell, investigated the ability of antibodies in the blood from people, who were vaccinated with the two-shot regimens, to neutralise the highly contagious Delta and Kappa variants, a statement said.

“There is no evidence of widespread escape suggesting that the current generation of vaccines will provide protection against the B.1.617 lineage,” the paper said, referring to the Delta and Kappa variants by a commonly used code.

However, the concentration of neutralising antibodies in the blood was somewhat reduced, which may lead to some breakthrough infections, they cautioned.