Researchers have found that T cells – one of the body’s key defences against Covid-19, can mount an effective immune response against Omicron, if antibodies fail to do that.

T cells, generated both by vaccinations and Covid-19 infections, have been shown to be critical in limiting progression to severe disease by eliminating virus-infected cells and helping with other immune system functions.

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Preliminary studies have reported that Omicron (fast becoming the most dominant circulating strain globally) can escape antibodies produced by vaccination or natural Covid-19 infection, raising concerns about the increased possibility of reinfection and breakthrough cases.

But, Omicron is unlikely to be able to evade T cells, according to the new study led by researchers from the University of Melbourne and Hong Kong University of Science and Technology (HKUST).

“Despite being a preliminary study, we believe this is positive news. Even if Omicron, or some other variant for that matter, can potentially escape antibodies, a robust T cell response can still be expected to offer protection and help to prevent significant illness,” said Professor Matthew McKay from the University of Melbourne.

In the study published in the peer-reviewed journal Viruses, the team analysed over 1,500 fragments of SARS-CoV-2’s viral proteins, called epitopes, that have been found to be recognised by T cells in recovered Covid-19 patients or after vaccination.

The results showed that only 20 per cent showed mutations associated with Omicron.

Even then, these mutations do not necessarily mean the virus will be able to evade the body’s T cells.

“Among these T cell epitopes that have Omicron mutations, our further analysis revealed that more than half are predicted to still be visible to T cells. This further diminishes the chance that Omicron may escape T cells’ defences,” said Ahmed Abdul Quadeer, research assistant at HKUST.

Further, the team broadened their analysis to other virus proteins, they found an overwhelming majority (more than 97 per cent) of non-spike T cell epitopes do not encompass mutations associated with Omicron.

“These results overall, would suggest that broad escape from T cells is very unlikely,” McKay said.

“Based on our data, we anticipate that T cell responses elicited by vaccines and boosters, for example, will continue to help protect against Omicron, as observed for other variants. We believe this presents some positive news in the global fight against Omicron.”