New Delhi: Amid a global concern involving the Delta (B.1.617.2) variant of Covid-19, the latest study conducted by the Indian Council of Medical Research (ICMR) has said that Covid-19 recovered individuals with one or two doses of vaccine had relatively higher protection against B.1.617.2 in comparison to the participants who were administered either one or two doses of Covishield.
The study titled "Neutralization of Delta variant with sera of Covishield vaccines and Covid-19 recovered vaccinated individuals", was conducted by ICMR-NIV, Pune. The study said that the recent emergence of B.1.617 lineage has created grave public health problems in India. The lineage further mutated to generate sub-lineage B.1.617.1 (Kappa), B.1.617.2 (Delta), B.1.617.3. "The Delta variant has slowly dominated the other variants including B.1.617.1. The high transmissibility associated with Delta variant has led to the second wave of the pandemic in India which affected millions of people," the study said.
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Besides this, a variant of concern has been reported to show lower neutralization to several approved vaccines. "This has led to breakthrough infections after completion of vaccination regimen," the study said highlighting its findings of immune response in sera of the Covishield vaccinated individuals. The findings of the study demonstrated that the breakthrough cases and the Covid-19 recovered individuals with one of two doses of vaccine had relatively higher protection against Delta variants in comparison to the participants who were administered either one of two doses of Covishield.
The study indicates that sera of Covid-19 recovered patients who were vaccinated with either one of two doses and breakthrough had higher neutralizing antibodies (NAb) titres relative to Covid-19 negative participants. "The significantly higher NAb titers in sera of participants of Covid-19 recovered as compared to Covid-19 negative highlights the fact that even one dose of vaccine in the convalescent patient is enough to provide effective protection against reinfection of SARS-CoV-2 or protection against newly emerging variants," the study said.
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"Prior vaccination results in less severe disease against subsequent infection provide evidence that both humoral and cellular immune response plays an important role in protection," the study said. After it was first detected in India, the Delta variant got a foothold in over 92 countries. The newly emerged SARS-CoV-2 variants have led to breakthrough infections after completion of the vaccination regimen.
"We have found that antibodies can have multiple other modes of action that are primarily mediated IgG1 and IgG3 subclass antibodies. Priming of the immune system memory is established by natural infection or vaccination," the study said. It further said that long term follow-up of participants could help understand the impact of natural infection and vaccination on long term protection from SARS-CoV-2 offered by Covishield.
"Monitoring of breakthrough infections would make understand the impact of new variant or VOC on the escape of vaccine-induced immunity," the study further said.
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