''Here, we have evaluated the IgG antibody titer and neutralizing potential of sera of COVID-19 naive individuals full doses of BBV152 vaccine, COVID-19 recovered cases with full dose vaccines and breakthrough cases post-immunization BBV152 vaccines against Delta, Delta AY.1 and B.1.617.3.,'' the study said.

The recent emergence of the SARS-CoV-2 Variant B.1.617.2 (Delta) variant with its high transmissibility has led to the second wave in India.

Covaxin, a whole-virion inactivated SARS-CoV-2 vaccine used for mass immunization in the country, showed a 65.2 per cent protection against the Delta variant in a double-blind, randomized, multicentre, phase 3 clinical trial.

Subsequently, Delta has further mutated to Delta AY.1, AY.2, and AY.3.

Of these, AY.1 variant was first detected in India in April 2021 and subsequently from 20 other countries as well, the study said.

The study is a pre-print and has not been peer reviewed.

Covaxin demonstrated 77.8 per cent effectiveness against symptomatic COVID-19 and65.2per centprotection against the B.1.617.2 Delta variant, Bharat Biotech had said while concluding the final analysis of Covaxin efficacyfrom Phase3 trials on July 3.