The degree of efficacy of the vaccines against the ‘variant of concern’ has been the ‘cause of concern’ for everyone. The Delta variant which has spread to 99 countries is a variant of concern and was also responsible for the second wave in India. Delta variant has also been identified as the leading cause of breakthrough infections globally among vaccinated individuals. Recently, the Delta variant has mutated to Delta AY.1, AY.2 and AY.3. Of these, Delta AY.1 variant (Delta Plus) was first detected in India in April 2021 and subsequently, from 20 other countries as well.
However, a study conducted by the Indian Council of Medical Research and National Institute of Virology has said that Bharat Biotech’s Covaxin is found to be effective against the Delta and Delta plus variant. The study released on Monday showed that Covaxin provides 65.2 per cent protection against the Delta variant which was first detected in India. The Delta variant has also been identified as the leading cause of breakthrough infections globally among vaccinated individuals, the study said. The study said that a minor reduction in the neutralising antibody titer in Covid-19 recovered cases and full BBV152 vaccinated and post immunized infected cases was observed but the vaccine was found to be effective against the Delta, Delta AY.1 and B.1.617.3 variants.
The study was published as a pre-print on bioRxiv and said that Sera of vaccines among Covid naïve recovered cases with full vaccination and breakthrough cases demonstrated 1.3, 2.5 and 1.9-fold reduction against Delta variant in comparison to B.1 variant respectively.
This demonstrates the possible role of memory cells in immune-boosting with post-infection or infection after immunization.
The comparative analysis of all the groups revealed that the B.1.617.3 seems to be less susceptible to neutralization followed by Delta AY.1 and Delta variants compared to B.1, the study said.
Meanwhile, two shots of AstraZeneca which is the same as the Covishield vaccine was found to be 67 per cent effective against the Delta variant according to a study published in the New England Journal of Medicine.
Dr Samiran Panda, head of epidemiology and communicable diseases, ICMR, told, “Our research showed that Covaxin could still neutralise Delta, AY.1 and B.1.617.3 variants.” Concluding the same Dr Panda said, “The bottomline is that Covaxin is effective and slight reduction in neutralisation antibody titres is not going to be detrimental for the vaccination programme.”
Lead author Dr Pragya Yadav said a minor reduction was observed in the neutralising antibody titer in Covid- 19 recovered cases, fully vaccinated and post immunised infected cases as compared to Covid-19 naive vaccinated individuals.
“However, with the observed high titers, the sera of individuals belonging to all the groups in the study would still neutralise the Delta, Delta AY.1 and B.1.617.3 variants effectively,” Dr Yadav said.
Although, as per the Bharat Biotech’s concluding final analysis of Covaxin efficacy from Phase3 trials on July 3, Covaxin demonstrated 77.8 per cent effectiveness against symptomatic COVID-19 and 65.2 per cent protection against the B.1.617.2 Delta variant.
Despite the sera of Covid-recovered cases with vaccinations and breakthrough cases of infection showing considerable reduction in the neutralisation antibody titre, Covaxin vaccine could still neutralise Delta, AY.1 and B.1.617.3 variants.
