How have some people avoided getting Covid-19?

Dozens of Brits have had four bouts of Covid-19 and thousands more have been infected three times, according to official data.

As the pandemic entered a third year, figures from the UK Health Security Agency (UKHSA) showed that 62 people had reported four positive Covid tests, each at least 90 days apart. 

But while many people have been re-infected multiple times, others appear to have avoided catching the coronavirus despite having come into close contact with cases – a disparity that scientists have struggled to explain. Here are some of the more plausible theories. 

Genetic resistance

An international consortium of researchers have launched a study to investigate whether a small proportion of people might be genetically resistant to Covid-19. Identifying such protective genes could lead to the development of new treatments for the coronavirus.

The scientists made a global appeal last October to find apparently Covid-resistant people to take part in the study, with the goal of enlisting a total of at least 1,000. “Of particular interest are people who shared a home and bed with an infected partner – pairs known as discordant couples,” reported scientific journal Nature.

The team, from ten research centres worldwide, had already recruited around 500 potential candidates. And within two weeks of launching their hunt, another 600 people had reportedly stepped forward offering to sign up.

“I did not think for one second that people themselves, exposed and apparently not infected, would contact us,” said study co-author Jean-Laurent Casanova of the Rockefeller University in New York.

The possible resistance that the study participants may have “is known to exist for other diseases, including HIV, malaria and norovirus”. The Guardian’s science correspondent Linda Geddes reported.

“In these cases, a genetic defect means some people lack a receptor used by the pathogen to enter cells, so they cannot be infected,” Geddes explained.

Study leader András Spaan, a professor at the Rockefeller University in New York, said that “it could well be that, in some individuals, there is such a defect in a receptor used by Sars-CoV-2”, the virus that causes Covid-19.

However, Spaan “thinks it is unlikely that the majority of those who have avoided Covid are genetically resistant, even if they have some partial immune protection”, said Geddes.

Common cold theory

A study led by a team from Imperial College London found that people who have fought off common colds may have a lower risk of catching Covid-19.

Article source: https://www.theweek.co.uk/news/science-health/956261/how-have-some-people-avoided-covid