The domestically developed Covaxin is effective against the Delta plus variant of Covid-19, claims Indian Council of Medical Research (ICMR) in its study released on Monday.Covaxin is developed by the Bharat Biotech in collaboration with ICMR and National Institute of Pune.The study states: "The sera of individuals who were fully immunized (with 2 doses) didn't show significant fold-reduction in the NAb titer against Delta, Delta AY.1 and B.1.617.3."Delta Plus is a mutated form of the Delta variant and was first discovered in India. It is characterised by increased transmissibility and spike protein mutations.The study points that Delta variant with its characteristic spike protein mutations has mutated further into four sub-lineages with an additional mutations which are associated with higher transmission and probable immune escape.Last week, Union Science and Technology Minister Jitendra Singh informed parliament last week that 70 cases of the Delta Plus variant were found by INSACOG, a group of 28 laboratories involved in genome sequencing.Covaxin along with other two vaccines -- Covishield and Russia's Sputnik -- has formed the trio for India's massive vaccination drive against the virus.The research further states, "A significant increase in the NAb titer against B.1 variant in recovered cases with vaccination and breakthrough cases was observed compared to the Covid-19 native vaccines. Similarly, a significant increase in NAb titer was also observed among these two groups against Delta, Delta AY.1 and B.1.617.3 variants.""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 variant seems to be less susceptible to neutralization followed by Delta AY.1 and Delta variants."The study on efficacy analysis further establishes Covaxin to be 93.4 per cent effective against severe symptomatic Covid-19 cases and 63.6 per cent protection against asymptomatic Covid-19.