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Updated July 4th, 2021 at 12:59 IST

ICMR study: 'COVID-recovered more protected against Delta variant' post-vaccination

In a significant revelation, a recent ICMR study has revealed that COVID-19 recoverees and breakthrough cases were better protected from COVID-19 Delta variant

COVID-19, ICMR
IMAGE: PTI | Image:self
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In a significant revelation, a recent ICMR study has revealed that COVID-19 recoverees and breakthrough cases were better protected from the COVID-19 Delta variant than those who have received one or two doses of the Covishield vaccine. Analysing five categories of inoculated groups, ICMR has highlighted the 'increased susceptibility of the population who has been immunized with even both doses of the vaccine with Delta variant'. The study titled '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 and has been uploaded to bioRxiv preprint server, for peer-review.

ICMR study on Delta variant post-vaccination

ICMR study has categorised its groups into five types with 31 subjects each:

  • One dose vaccinated
  • Two doses vaccinated
  • COVID-19 recovered plus one dose vaccinated
  • COVID-19 recovered plus two doses vaccinated (studied four weeks post-vaccination)
  • Breakthrough COVID-19 cases (studied two weeks after taking two doses)

What has the study revealed?

The study stated, "B.1 (normal COVID variant) were not observed in 11/31 (35.5%) participants in category I. Similarly, neutralizing antibody (NAb) against the B.1.617.2 (Delta variant) were not observed in 18/31 (58.1%) and 5/31 (16.1%) participants of categories I and II respectively. Moreover, NAb titers for B.1.617.2 (Delta) relative to B.1 (normal) were reduced in the sera of the participants belonging to categories I (78%), II (69%), III (66%), IV (38%) and V (47%)". 

This meant that antibodies produced after vaccination against the Delta variant were less as compared to the normal variant (B.1). Those receiving both doses of vaccine were more immune from both B.1 and B.1.617.2 strains as compared to inoculated with a single dose. The reduction in susceptibility was seen most in breakthrough cases compared to those inoculated with one or two doses of Covishield. The study concluded that antibodies may highest among breakthrough cases due to spike-specific T-cell responses.

"The significantly higher NAb titers in sera of participants of COVID-19 recovered (categories III and IV) as compared to COVID-19 negative (categories I and II) highlights the fact that even one dose of vaccine in convalescent patients is enough to provide effective protection against re-infection of SARS-CoV-2 or protection against newly emerging variants," stated the study. ICMR has assured that both vaccines (Covishield and Covaxin) were effective against Delta variant and the study to verify their effectiveness against the Delta Plus variant was under study.

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Published July 4th, 2021 at 12:59 IST

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