Prior Covid infection helps T Cells offer high protection against omicron

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T cells play a key role in the development of long-term immunity to coronavirus
T cells play a key role in the development of long-term immunity to coronavirus

People who have previously had Covid or been vaccinated have T cells in their system which work well against omicron, a new study suggests.

T cells are a form of immunity that are longer-lasting than antibodies, and although they do not stop infection, they prevent the virus from causing severe disease and death.

“We report here that SARS-CoV-2 spike-specific … T cells induced by prior infection or [Pfizer] vaccination provide extensive immune coverage against [omicron],” the researchers, led by the Karolinska Institute in Stockholm, write in their study, published in Nature Medicine.

There are two forms of T cells, called CD4+ and CD8+, which are better known as T helper and T killer cells, respectively. The former help other cells tackle the virus, whereas the latter directly kill human cells which have been breached by the pathogen.

In a person who had previously caught Covid, 84 per cent of their T helper cells worked against omicron and 70 per cent of their T killer cells did the same.

However, people who had received the vaccine showed even better results, with 91 per cent of their T helper and 92 per cent of their T killer cells working against omicron.

“Collectively, our data indicate that established SARS-CoV-2 spike-specific CD4+ and CD8+ T cell responses, especially after [Pfizer] vaccination, remain largely intact against [omicron],” the researchers write.

The findings are the latest to emphasise the importance of T cells in the fight against Covid.

Earlier in the week, a study from Imperial College London and published in Nature Communications found T cells from some common colds work against SARS-CoV-2, the virus which causes Covid.

Dr Rhia Kundu, first author of the Imperial study, said: “We found that high levels of pre-existing T cells, created by the body when infected with other human coronaviruses like the common cold, can protect against Covid-19 infection.

“While this is an important discovery, it is only one form of protection, and I would stress that no one should rely on this alone.”

T cells are more versatile and wide-reaching than antibodies because they target a different part of the coronavirus which is not as changeable as the spike protein: the part of the virus that antibodies focus on and becomes altered on new variants.

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