Health

Common cold may have given Britons protection against Covid



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ome people who develop high levels of natural immunity after having a common cold are less likely to catch Covid, London researchers suggested today.

They said the study was the first evidence of the ability of T cells – white blood cells that can kill or respond to other cells infected with a virus – to protect against Covid.

This could act as a blueprint for a second generation “universal” vaccination effective against all variants, including Omicron.

But experts warned that it would be a “grave mistake” to rely on a previous cold as the only protection against Covid, as only about 10 per cent of colds were caused by coronaviruses.

Today’s research, led by Imperial College London, shows how the presence of T cells that have been induced by a “coronavirus cold” can reduce the risk of becoming infected with covid when exposed to the virus.

Dr Rhia Kundu, from Imperial’s National Heart & Lung Institute, said: “Being exposed to the SARS-CoV-2 virus doesn’t always result in infection, and we’ve been keen to understand why.

“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. Instead, the best way to protect yourself against Covid-19 is to be fully vaccinated, including getting your booster dose.”

The Imperial research, published in Nature Communications, began in September 2020 when most people in the UK had neither been infected nor vaccinated against Covid.

It included 52 people who lived with someone with a PCR-confirmed Covid infection and who had therefore been exposed to the virus. The participants did PCR tests at the outset and four and seven days later, to determine if they developed an infection.

Analysis of blood samples found that in 26 people who did not become infected with Covid, there were significantly higher levels of pre-existing T cells, compared with levels in 26 people who did catch Covid.

Unlike current vaccines, these T cells targeted internal proteins within the virus, rather than the spike protein on its surface.

The researchers say internal proteins offer a new vaccine “target” that could provide long-lasting protection because T cell responses last longer than antibody responses, which wane within a few months of vaccination.

Professor Ajit Lalvani, senior author of the study, said: “Our study provides the clearest evidence to date that T cells induced by common cold coronaviruses play a protective role against [covid] infection.

“These T cells provide protection by attacking proteins within the virus, rather than the spike protein on its surface.

“New vaccines that include these conserved, internal proteins would therefore induce broadly protective T cell responses that should protect against current and future SARS-CoV-2 variants.”

Dr Simon Clarke, of the University of Reading, who was not involved in the study, said: “Although this is a relatively small study, it adds to our understanding of how our immune system fights the virus and shows that future vaccines might benefit from targeting components in addition to the spike protein.

“These data should not be over-interpreted. It seems unlikely that everyone who has died, or had a more serious infection, has never had a cold caused by a coronavirus. It could be a grave mistake to think that anyone who has recently had a cold is protected against Covid-19, as coronaviruses only account for 10-15 per cent of colds.

“Similarly, there is no measurement of how much protection the reported effect gives people and a link is only hinted at – it has not been proven conclusively.”



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