Exposure to common cold could provide immunity to Covid-19

Exposure to the common cold could provide some measure of immunity to Covid-19, a new study suggests.

The key to this immunity lies in T-cells, a type of white blood cell that helps the immune system fight off viruses, which experts believe may have just as important a role to play as antibodies in fighting off the virus.

Researchers at Tubingen University in Germany compared blood cells from patients who had recovered from Covid-19 with those that had not had the disease.

Their research, published on the pre-print server Research Square and not peer reviewed, showed that 81 per cent of the 185 people they tested who had not had the disease had a T-cell response to Sars-Cov-2, the virus that causes Covid-19. 

And this immune response was linked to previous exposure to common cold coronaviruses, the researchers found.

This is not the first time that exposure to the common cold has been linked to resistance to Covid-19 and there is some speculation that this is one of the reasons why children and younger people are seemingly more immune to the disease than older adults. 

Professor Sir John Bell, Regius Professor of Medicine, University of Oxford told the House of Lords Science and Technology Select Committee  last month that younger people may have T-cells that “provide some protection against this pathogen”.

Two studies published last month also showed that T-cells were important for fighting Covid-19 among both infected and uninfected individuals, with exposure to previous coronaviruses an important factor. 

This German study also showed that individuals who had had a mild case of the disease also had a T-cell response, suggesting that while T-cells may not prevent people from catching the disease, they may ensure that people only get a mild dose. 

This T-cell response has been seen in other coronaviruses, Mers and Sars, where a heightened immune response has been shown to both aid recovery and provide long-term protection against the disease. 

The findings may also go some way to explaining why some people who believe they have had the disease because they have experienced the classic symptoms of shortness of breath, tiredness and loss of taste and smell have tested negative in antibody tests, the researchers said. 

The increasing understanding of the role of T-cells in fighting the disease will also aid the development of vaccines, treatments and diagnostics, the researchers wrote. 

The research showed that more intense T-cell responses were not linked to disease severity, meaning that treatments that induce a strong response will not aggravate the disease, the researchers said. 

Professor Francois Balloux, director of University College London's Genetics Institute, who was not involved in the study, said on Twitter the research was interesting and the discovery of pre-existing T-cell immunity was "good news".