T cells come to the rescue as studies show they buck Omicron Covid variant

An unsung arm of the immune system appears to protect against severe disease with the Omicron variant even when antibodies wane, helping explain why a record wave of infections hasn’t engulfed hospitals so far.

T cells, the body’s weapon against virus-infected cells, were primed enough by vaccination that they defended against Omicron in separate studies from Erasmus University in the Netherlands and the University of Cape Town in South Africa.

The findings could help explain why the wave of Omicron cases hasn’t so far caused a surge in mortality. Unlike antibodies, T cells target the virus’ whole spike protein, which remains largely similar even in the highly mutated Omicron.

T cell responses

The Dutch researchers looked at 60 vaccinated health-care workers and found that while their antibody responses to Omicron were lower or non-existent compared with the Beta and Delta variants, T cell responses were largely unaltered, “potentially balancing the lack of neutralising antibodies in preventing or limiting severe Covid-19.”

Also see: Community spread of Omicron can overwhelm hospitals: Experts

The study from the University of Cape Town’s Institute of Infectious Disease and Molecular Medicine looked at patients who had recovered from Covid or been vaccinated with shots from Pfizer and partner BioNTech SE or Johnson & Johnson. They found that 70–80 per cent of the T cell responses they assessed held up against Omicron.

Minimise damage

Recent weeks have brought evidence that the new strain can erode vaccine protection, prompting governments to push for booster shots to raise the level of antibodies that can fight off the variant.

But immune protection has several layers. While antibodies block infection, T cells kill infected cells, preventing the virus from spreading and causing worse disease, Wendy Burgens, one of the University of Cape Town study authors, wrote on her Twitter account Virus Monologues.

Also see: Covid-19 vaccination: India has administered over 144.5 crore total doses so far

“They can’t prevent you from getting infected, but they can minimise the damage that comes afterwards,” she said.

T cells are white blood cells that can remember past diseases, kill virus-infected cells and rouse antibodies to marshal defences. People infected with another coronavirus that was responsible for the SARS outbreak in 2003, for example, were found to still have a T-cell response to the disease 17 years later.

Booster vaccine doses

Another study found that booster shots increased the production of T cells in the face of an Omicron infection. Giving J&J’s vaccine to people who had previously received a messenger RNA shot yielded better results, though a third dose of Pfizer and BioNTech’s immunisation also led to higher levels of cellular immunity and neutralising antibodies after one month, according to findings from Beth Israel Deaconess Medical Center.

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