Current Covid Vaccines May Protect From Severe Disease Caused By Omicron: Study

Washington: Current COVID-19 vaccines prompt the body to make effective, long-lasting T cells against SARS-CoV-2 that can recognise variants of concern, including Omicron, and protect from severe disease, a study has found. The research, published in the journal Cell, also shows that fully vaccinated people have fewer memory B cells and neutralising antibodies against the Omicron variant. Both T and B cells play an important role in the immune response against an infection. Scientists at La Jolla Institute for Immunology (LJI) in the US tested four COVID-19 vaccines – Pfizer-BioNTech, Moderna, J&J/Janssen, and Novavax.

The vast majority of T cell responses are still effective against Omicron, said study co-leader Alessandro Sette, a professor at LJI.

These cells won’t stop you from getting infected, but in many cases they are likely to keep you from getting very ill, said co-author Shane Crotty, a professor at LJI.

This is true in all the type of vaccines studied, and up to six months after vaccination, said LJI instructor Alba Grifoni, who co-led the work. These data come from adults who were fully vaccinated, but not yet boosted. Without enough neutralising antibodies, Omicron is more likely to cause a breakthrough infection, the researchers said. Fewer memory B cells means the body will then be slower to churn out additional neutralising antibodies to fight the virus, they said.

Also Read: Dangerous To Assume Omicron Will Be The Last Variant; We Can End The Acute Phase Of COVID-19 This Year: WHO Chief

Most of the neutralising antibodies, i.e., the antibodies that work well against SARS-CoV-2, bind to a region called the receptor binding domain, or RBD, said LJI instructor Camila Coelho, another co-first author of the study.

Our study revealed that the 15 mutations present in Omicron RBD can considerably reduce the binding capacity of memory B cells, compared to other SARS-CoV-2 variants such as Alpha, Beta and Delta, Coelho said.

The good news, the researchers said, is that neutralising antibodies and memory B cells are just two arms of the body’s adaptive immune response. In a person exposed to SARS-CoV-2, T cells do not prevent infection, they said. However, T cells patrol the body and destroy cells that are already infected, which prevents a virus from multiplying and causing severe disease, the researchers said. The team noted that the “second line of defence” from T cells helps explain why Omicron infections are less likely to lead to severe disease in fully vaccinated people. To know whether the vaccine-induced T cells were actually effective against variants such as Delta and Omicron, the scientists took a close look at how these cells responded to different viral “epitopes.” Every virus is made up of proteins that form a certain shape or architecture. A viral epitope is a specific landmark on this architecture that T cells have been trained to recognise.

Also Read: COVID-19 And Omicron: About Time You Break Up With A Cloth Mask? Here’s What Experts Have To Say

The study shows that while the architecture of Omicron is different enough to evade some neutralising antibodies and memory B cells, memory T cells still do a good job of recognising their targets. Overall, at least 83 per cent of the CD4+ (helper) T cell responses and 85 per cent of the CD8+ T cell responses stayed the same, no matter the vaccine or the variant. The researchers noted that the memory B cells that do bind Omicron are likely to also contribute to protection against severe disease. However, they emphasised that no one should count on T cell protection alone. The study sheds light on immunity at the population level, but individual immune responses vary, and relying on one’s untested immune system to fight COVID is a roll of the dice, they added.

(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)

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