Covid Vaccine: ICMR Study Reveals Efficacy of Covishield Against Delta Variant

Covid Vaccine: No antibodies were found against Delta variant in 16 percent samples after two doses of Covishield.

Covid Vaccine: ICMR Study Reveals Efficacy of Covishield Against Delta Variant

According to a new study by the Indian Council of Medical Research (ICMR), the neutralising antibodies against the Delta variant (B1.617.2), was not observed in 16.1 percent of people who had received both doses of Covishield COVID-19 vaccine and in 58.1 percent of those who were given the first dose.

The study, which is yet to be peer-reviewed, was posted on bioRxiv preprint server last week.

The researchers also observed that a prior infection along with vaccination produced much higher titres of neutralising antibodies.


In this study, the researchers evaluated immune response in sera of the Covishield vaccinated individuals belonging to five categories:

  1. One dose vaccinated

  2. Two-dose vaccinated

  3. Covid recovered plus one dose vaccinated

  4. Covid recovered plus two doses vaccinated

  5. Breakthrough Covid cases

The study found that breakthrough cases and COVID-19 recovered individuals with one or two doses of vaccine have relatively higher protection against Delta variant in comparison to those administered either one or two doses of Covishield.

"Prior vaccination results in less severe disease against subsequent infection provide evidence that both humoral and cellular immune response play an important role in protection," it further said.

It also found that the neutralising antibodies were lower against the Delta variant as compared to the B1 variant that led to the first wave of infections in India.

Compared to B1, the neutralising antibody titres against the Delta variant were 78 percent less in those who received one shot, 69 percent in those who got two doses, 66 percent in those who had the infection and received one shot, 38 percent in those who had the infection and received both shots.

The SARS-CoV-2 lineage B.1.617 was initially detected from India during October 2020. It has further mutated as sub lineages B.1.617.1 (Kappa), B.1.617.2 (Delta) and B.1.617.3 variant.

The Delta variant which fuelled the devastating second wave in India has been reported to be 60 percent more transmissible than the Alpha variant.

The World Health Organisation (WHO) has designated Delta variant as a Variant of Concern (VOC).

It has now sprad to over 92 countries worldwide and has dominated over the Alpha variant in the UK.

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