Immune response induced by Omicron effectively neutralise Delta: ICMR study

An ICMR study has demonstrated that individuals infected with Omicron have significant immune response which could neutralise not only the Omicron, but also other variants of concern, including the most prevalent Delta variant.

It suggests that the immune response induced by the Omicron could effectively neutralise the Delta variant, making the re-infection with Delta variant less likely, thereby displacing the Delta as dominant strain, the study said emphasising upon the need for Omicron-specific vaccine strategy.

The study was conducted on 39 individuals, of which 25 had taken both the doses of AstraZeneca COVID-19 vaccine, eight people had taken double dose of Pfizer jab, while six were unvaccinated.

Also, 28 of these 39 were mainly foreign returnees from the UAE, South/West/East Africa, Middle East, the US and the UK, and 11 people were their high-risk contacts. All these individuals were infected with Omicron variant.

The study assessed the IgG antibody and Neutralizing Antibody (NAb) response in the people with breakthrough and natural COVID-19 infections.

"Our study demonstrated substantial immune response in the individuals infected with Omicron. The neutralizing antibodies could effectively neutralize the Omicron and other variants of concern (VOCs), including the most prevalent Delta variant," the study stated.

The main limitation of this study are lesser participants in the unvaccinated group and the shorter window period post infection. This could be the important reason for the low immune response specifically in the unvaccinated individuals against Omicron, the scientists stated.

The study has been conducted by ICMR scientists, including Pragya D Yadav, Gajanan N Sapkal, Rima R Sahay and Priya Abraham. It is yet to be peer-reviewed and has been released on bioRxiv preprint server on January 26.