Researchers warned that 'no one should rely on this alone'
A new peer-reviewed study has found that people with high levels of T-cells from common colds are less likely to catch Covid.
T-cells are a type of white blood cell that help protect the body from infection, and are induced by common cold infections.
Researchers at Imperial College London say the findings can help in the development of future vaccines against Covid-19, which could give longer-lasting immunity and be more effective against new variants.
But they added that no one "should rely on this alone" as protection against the virus.
Dr Rhia Kundu, first author of the study, 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.
Whilst acknowledging that this is an "important discovery", Dr Kundu emphasised that "no one should rely on this alone" and that the "best way to protect yourself against COVID-19 is to be fully vaccinated."
The study began in September 2020, and involved 52 people who lived with someone who was infected with Covid.
The participants did PCR tests at the start and then did PCRs four and seven days later to see if they had caught the virus.
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Blood samples were taken from the 52 people within six days of them being exposed to the virus to enable the researchers to analyse the levels of pre-existing T cells induced by previous common cold coronavirus infections that also cross-recognise proteins of COVID.
They found that there were much higher levels of these T-cells in the 26 people who did not catch the virus, compared to the 26 who did.
It's thanks to the fact that the T-cells target internal proteins within the virus, rather than the spike protein on its surface, something which vaccines aren't currently able to do.
Professor Ajit Lalvani, senior author of the study and Director of the NIHR Respiratory Infections Health Protection Research Unit at Imperial, said it was the "clearest evidence to date" that T cells induced by the common cold play a protective role against Covid-19.
He said: "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."
