The common cold can be caused by coronaviruses – not ­Covid-19, but coronaviruses from the same family.

And there’s a theory that ­antibodies created by the immune system during ­infection with common cold coronaviruses could protect against Covid-19.

This might explain why some people seem immune to Covid as scientists at University College London and the Francis Crick Institute claim.

In response to infection with a virus, the immune system creates antibodies to help fight it. These antibodies remain in the blood for a period after infection, and in the case of ­reinfection, they are able to tackle the virus again.

The researchers have found that some people, notably children, have antibodies to SARS-CoV-2 in their blood, despite not ever being infected with the virus.

These antibodies are likely the result of exposure to other coronaviruses, which have a structure similar to Covid-19 and cause a cold.

However, a small ­fraction of adult donors, about one in 20, also had ­antibodies that ­cross-reacted with Covid-19, and this wasn’t dependent on a recent infection with a common cold coronavirus.

Amazingly these cross-reactive ­antibodies were found much more frequently in children aged six to 16.

Lead author, Kevin Ng, PhD student at the Crick in London, said: “Our results show that children are much more likely to have these ­cross- reactive antibodies than adults… it could be down to children being more regularly exposed to other coronaviruses.

“These higher levels we observed in children could also help explain why they are less likely to become severely ill with Covid-19. There is no evidence yet, however, that these antibodies prevent SARS-CoV-2 infection or spread.”

The scientists found the cross-reactive ­antibodies target the S2 subunit of the spike on the virus surface.

Senior author, Professor George Kassiotis, of the Crick and UCL, said the S2 subunit, which lets the virus into cells, is sufficiently similar between common cold coronaviruses and Covid-19 for some antibodies to work against both.

He added: “This is exciting as ­understanding the basis for this activity could lead to vaccines that work against a range of coronaviruses, including the common cold strains, as well as SARS-CoV-2 and any future pandemic strains.”