Covid-19, we still don’t understand why some people don’t get sick

We all know a person who, defying all logic, has succeeded inundertaking to dodge COVID-19. Beyond factors such as prudence, luck or lack of friendsit is possible that the secret of these people’s immunity lies in theirs genes? And could it hold the key to fighting the virus?

In the early days of the pandemic, a small and close-knit community of scientists from around the world created an international consortium, renamed Covid Human Genetic Effortwhose goal was look for a genetic explanation why some people became seriously ill with Covid-19 while others coped with a mild cold.

Over time, the group noticed that some people were not infecteddespite repeated and intense exposures. The most interesting cases were those of partners of people who became seriously ill and ended up in intensive care: “We have found that some spouses, despite taking care of their husband or wife without having access to face masks, apparently they did not contract the infection “explains András Spaan, a clinical microbiologist at Rockefeller University in New York.

Spaan was commissioned to create a project segment for investigate apparently immune individuals. First, it was necessary to find a good number of subjects: for this purpose the team published an article in Nature Immunology in which he illustrated the study, adding a final line in which he specified that “subjects from all over the world are welcome“.

Volunteers from all over the world

The answer, Spaan says, it was overwhelming: “We have received literally thousands of emails”. The huge amount of people who rushed to sign up forced researchers to create a multilingual online survey. To date about 15 thousand applications arrived from all over the world.

The theory that these people may have pre-existing immunity is supported by historical examples. There are genetic mutations that confer natural immunity to HIV, al norovirus and to a parasite that causes the recurrent malaria. Why should Covid-19 be any different, the team thought? Yet, in the long history of immunology, the concept of innate resistance to infection it is quite new. Few scientists care. “It is such a niche field that even within the fields of medicine and research it is a bit ignored”he claims Donald Vinh, associate professor in the Department of Medicine at McGill University in Canada. Geneticists don’t see it as genetics, and for immunologists it’s not immunology. This despite the fact that there is a clear therapeutic goal: “If you can figure out why someone can’t get infected, then you can figure out how to prevent infection.”says Vinh.

But finding immune people is an increasingly difficult task. While many have volunteered, only a small minority meet the team’s stringent criteria, which is to have likely crossed the virus without developing antibodies (which would indicate an infection). The most promising candidates are those who, against all logic and succeeding, did not contract the disease despite being at high risk: health workers constantly exposed to positive patients, or people who have lived with – or better yet, shared a bed – with people whose infection was confirmed.

When he started looking for suitable people, the team also had to deal with mass vaccination programs. “On the one hand, a lot of people were getting vaccinated, which is great, don’t get me wrong – says Vinh -, but they are not the people we want “.

The arrival of Omicron

Then came the highly infectious Omicron variant: “Omicron really ruined the project, I have to be honest”explains Vinh. The variant has drastically reduced the shortlist of candidates. But Spaan the advent of Omicron in a more positive light: the fact that some subjects were not affected by the wave of the variant confirms the existence of an innate resistance.