People produced high levels of T cells when they had a common cold (Picture: Getty Images)
When someone catches a cold the defences their body generates may help ward off Covid-19, experts have suggested.
A small study, carried out by researchers at Imperial College London, investigated why some people didn’t catch the virus even after being exposed to it.
It found when people caught other coronaviruses, like the common cold, they produced high levels of T cells which could make them less likely to catch Covid-19.
But the experts stressed people should still get vaccinated as the best chance to protect themselves against the virus.
Dr Rhia Kundu, first author of the study published in journal Nature Communications, 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.’
Some people still don’t seem to catch Covid-19 even after being in direct contact with the virus (Picture: Getty Images)
Experts observed 52 people who lived with a confirmed case of Covid-19 back in September 2020 – before the vaccination programme was launched.
Those who participated carried out a PCR at the start of the study, and four and seven days later, to see if they also caught the virus.
Blood samples were taken during the first six days so researchers could analyse the levels of pre-existing T cells, induced by previous infections of coronaviruses like the common cold.
It was found there were significantly higher levels of T cells in the 26 people who did not catch Covid-19, than in the 26 people who did.
The authors said these T cells targeted internal proteins in the virus, rather than the spike proteins on the surface. Current vaccines only target the spike proteins, so new vaccines could potentially lead to longer-lasting protection.
Professor Ajit Lalvani, senior author of the study and director of the NIHR Respiratory Infections Health Protection Research Unit at Imperial, said: ‘Our study provides the clearest evidence to date that T cells induced by common cold coronaviruses play a protective role against Sars-CoV-2 infection.
‘These T cells provide protection by attacking proteins within the virus, rather than the spike protein on its surface.
‘The spike protein is under intense immune pressure from vaccine-induced antibody, which drives evolution of vaccine-escape mutants. In contrast, the internal proteins targeted by the protective T cells we identified mutate much less.
‘Consequently, they are highly conserved between the various Sars-CoV-2 variants, including Omicron. 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.’
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