ONE in four people may already be immune to coronavirus – without ever being infected, a new study has found.
Public Health England (PHE) followed nearly 2,850 key workers from the police, fire and health services to gauge levels of immunity to Covid-19.
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Researchers found that by June, a quarter had high levels of T-cells which recognised the virus.
It suggested they had some level of protection against the bug, yet nearly half had never been infected.
The experts believe they may have developed a level of immunity from similar coronaviruses – like the one that causes the common cold.
They followed up with the study sample after four months and found that no-one with a high T-cell count had caught Covid.
Dr Peter Wrighton-Smith, the CEO of Oxford Immunotec, the company that developed the T-cell test for trial, said that the results show that relying on antibody testing alone to see who is immune to the virus could underestimate the number of people who have immunity.
T-cells target and destroy cells in the body that become infected by the virus.
Previous studies on immunity have centered on antibodies.
Antibodies neutralise a virus before it is able to enter the cells of the body.
Data from the study found that none of the participants with high T-cell responses became infected with the virus in the following four months.
This, the experts claim, suggests that part of the immune system can protect people from the virus.
The study was published in medRxiv and has not yet been peer reviewed.
Commenting on the results Dr Wrighton-Smith said the people used in the study had all been frontline workers and were therefore more likely to have been exposed to the virus.
He said: “The implication is that there is a population of people who are protected from Covid who are not being picked up by the antibody studies.”
The experts stressed that the findings could mean that T-cells are longer lasting than antibodies or that people are left with immunity after suffering from similar coronaviruses such as the common cold.
Dr Wrighton-Smith added: “We are not picking up all cases with the antibody surveys – so more people may be protected than we thought.”
The lead author of the study, Dr David Wyllie, a consultant microbiologist at PHE said that just four months into the study, 20 of the participants had lower T-cell responses and had developed Covid, in comparison none of the individuals with high T-cell responses contracted the virus.
He said: “This suggests individuals with higher numbers of T-cells recognising SARS-CoV-2 may have some level of protection from Covid-19, although more research is required to confirm this.”
Reacting to the publication of the study, Professor Karol Sikora, a cancer expert at the University of Buckingham said the finding was “really good news”.
Prof Sikora has previously highlighted the importance of T-cells and tweeted: "This means almost certainly the T-cell response is innate – it is [triggered] by something people have been exposed to in the past.
“So when Corona comes along they are not susceptible.
“It suggests more people have protection than antibody surveys estimate, but also many probably have residual immunity to Covid-19 from other infections.
“T-cells have been overlooked for too long. This proves that has to change.”
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