COVID-19: Who is immune without having an infection?

The number of new COVID-19 cases is on the rise in many regions across the globe. But not everyone who comes into contact with SARS-CoV-2, the new coronavirus, develops COVID-19.

Stay informed with live updates on the current COVID-19 outbreak and visit our coronavirus hub for more advice on prevention and treatment.

A group of scientists from the Francis Crick Institute, in London, along with colleagues at University College London, both in the United Kingdom, may have found a clue as to why some people can fight off a SARS-CoV-2 infection better than others.

Their work recently appeared in the journal Science.
Surprise discovery

The research team originally set out to develop a high-sensitivity test to detect antibodies to the SARS-CoV-2 virus.

Scientists can use this type of test to establish whether a person has antibodies after they had COVID-19, which is a key piece of information for those trying to establish how long immunity may last after SARS-CoV-2 infection.

As part of their work, the scientists used serum samples provided by people who did not have COVID-19. To their surprise, they found antibodies that reacted to SARS-CoV-2 in some of the samples.

In their paper, the researchers describe a scientific theory that exposure to any of the common human coronaviruses, which can cause the common cold, may lead to immunity against the other common human coronaviruses. They refer to this as immune cross-reactivity.

here are four seasonal common human coronaviruses, all of which mostly cause mild disease. The vast majority of people have an infection with at least one of these viruses at some point.

Scientists already know that our bodies do not build up long-lasting immunity to these viruses, which is why a person can contract an infection with a common human coronavirus more than once in their lifetime.

But can a previous exposure to a common human coronavirus provide at least temporary protection against SARS-CoV-2?