Omicron Infection May Not Boost Immunity Levels in Unvaccinated People: Study

Researchers infected mice with Delta and Omicron to test whether their sera could neutralise other variants.

According to a new study from the US, if an unvaccinated person is infected with the Omicron variant of COVID-19, it may not generate broad immunity in their body to shield them against other variants.

However, if a vaccinated person is infected with Omicron, it can boost their existing immunity, and provide better protection against another infection, says the study conducted by a team comprising Nobel Laureate Jennifer Doudna, researchers from the University of California, San Francisco, University of California, Berkeley, California Department of Public Health, and COVID-19 testing startup Curative Inc.

The researchers infected mice with the Delta and Omicron variants to test whether their sera (a blood component) could neutralise or fight against the original virus, and the Alpha, Beta, Delta, and Omicron variants of COVID-19, The Indian Express reported.

It was found that the mice infected with Delta was best protected against other variants, except the Beta variant, which is known to be highly immune-evasive.

However, on being infected with Omicron, the mice could only effectively fight off the same variant, and did not fully protect them against other variants, according to the study.

After the mice study, the researchers used sera from vaccinated individuals, who still got the Delta and Omicron infections (breakthrough infection), to see how much protection they had against the wild type as well as all the other variants.

While the sera from those who had a Delta breakthrough infection could effectively neutralise all variants, the neutralisation for Omicron was low.

Further, according to The Indian Express, the researchers found that the sera from the Omicron breakthrough infection provided good protection against all variants, and stated, "These findings suggest that Omicron infection can effectively boost existing immunity conferred by the vaccination against other variants, eliciting 'hybrid immunity' that is effective against not only itself but also other variants."

Highlighting the importance of getting vaccinated, Dr Anurag Agarwal, Director of Institute of Genomics and Integrative Biology, was quoted as saying:

"Omicron is not nature's vaccine. Omicron infection does not give protection against infection by other variants, in unvaccinated people. Previously reported effects against Delta were due to enhancement of vaccine induced immune response that protects well against prior variants."

(With inputs from The Indian Express.)