A study by ICMR-NIV has shown that Covaxin (BBV152) is effective against the delta and delta plus variants of the coronavirus. However, it may need an additional booster after 2 doses, which is undergoing research.

The study, published as a preprint on August 1, 2021 in bioRxiv, evaluated the IgG antibody titer and neutralizing activity of the sera of COVID-19 naive individuals vaccinated with two doses of BBV152, Covid-19 recovered patients vaccinated with two doses of BBV152 and post-vaccine (two doses of BBV152) breakthrough cases against the delta (B.1.617.2), delta plus (AY.1) and B.1.617.3 variants of SARS-CoV-2.

A reduction in neutralizing activity was observed with the COVID-19 naive individuals fully vaccinated (1.3, 1.5, 1.9-fold), COVID-19 recovered cases with full immunization (2.5, 3.5, 3.8-fold) and breakthrough cases post-immunization (1.9, 2.8, 3.5-fold) against delta, delta AY.1 and B.1.617.3 respectively compared to B.1 variant.

When tested against the delta variant and its sublineages, the neutralising antibody titers were found to be reduced by several folds in patients who had recovered from Covid-19 and also in the fully vaccinated individuals compared to those who did not have Covid but had taken both the doses of the vaccine. However, these titers were still high enough to effectively neutralize the delta, delta AY.1 and B.1.617.3 variants.

BBV152 is a whole-virion inactivated SARS-CoV-2 vaccine adjuvanted with Algel-IMDG (an imidazoquinoline molecule chemisorbed on alum).

In a previous double-blind, randomized, multicentre, phase 3 clinical trial of 25,800 subjects, Covaxin had demonstrated 77.8% vaccine efficacy against symptomatic COVID-19 disease with 63.6% protection against asymptomatic COVID-19. The efficacy against severe symptomatic COVID-19 disease has been shown to be 93.4%. Covaxin has also demonstrated 65.2% protection against the delta variant.

The delta variant (B.1.617.2) is one of the three sublineages of the B.1.617 variant (double mutant, first detected in Maharashtra) and is the most dangerous. The B.1.617.1 strain (kappa) is a variant of interest, while the B.1.617.3 lineage is a variant under monitoring. AY.1 (delta plus), AY.2 and AY.3 have been identified as further sublineages of the delta variant. Of these, delta plus was labelled as a variant of concern in the country. But cases due to AY.1 have now declined to less than one percent.

The delta variant, which is a highly transmissible strain of SARS-CoV-2, was responsible for the deadly second wave in the country, except in parts of north India where the alpha strain is still prevalent. It has rapidly replaced the alpha strain (B.1.1.7, first detected in the UK) to become the dominant circulating variant globally.

India continues to record around 30,000 -35,000 daily new cases, on an average, which are due to infection with the delta variant. It has also shown miniscule immune escape and is the cause of most breakthrough infections. Hence, these observations that Covaxin can effectively neutralise the delta and delta plus variants are very encouraging and good news for the vaccination program. Along with vaccination, adherence to Covid-appropriate behavior is necessary. It is not a choice between “either” or “or”.

(Source: bioRxiv, Posted August 01, 2021, doi: https://doi.org/10.1101/2021.07.30.454511)