Indian Council of Medical Research has found in its latest study that individuals who have recovered from COVID-19 and have been administered one or two doses of the Covishield vaccine have a relatively higher protection against the virulent Delta variant in comparison to those administered either one or two doses of the Covishield but have not contracted the coronavirus infection.
According to the ICMR study, this provides evidence that both humoral and cellular immune response play an important role in protection. The study is yet to be peer-reviewed and was posted on bioRxiv preprint server.
The study ‘Neutralisation of Delta Variant with Sera of Covishield vaccines and COVID-19 Recovered Vaccinated Individuals’ has been done by scientists from the ICMR, National Institute of Virology, Pune, and Department of Neurosurgery, Command Hospital (Southern Command), Armed Forces Medical College, Pune. The recent emergence of B.1.617 lineage has created grave public health problem in India.
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The lineage further mutated to generate sub-lineages B.1.617.1 (Kappa), B.1.617.2 (Delta) and B.1.617.3. The Delta variant appears to have slowly dominated the other variants. With this, the World Health Organisation has described this sub-lineage as a variant of concern, the study stated.
“The high transmissibility associated with the Delta variant led to the second wave of the pandemic in India which affected millions of people. Besides this, variant of concern has been reported to show lower neutralisation to several approved vaccines. This has led to breakthrough infections after completion of vaccination regimen," it said.
There is limited information available on the duration of protective immune response post-infection, vaccination or breakthrough infection with SARS-CoV-2. The study evaluated immune response in sera of the Covishield vaccinated individuals belonging to categories- one dose vaccinated, two doses vaccinated, COVID-19 recovered plus one dose vaccinated, COVID-19 recovered plus two doses vaccinated and breakthrough COVID-19 cases.
