We all know some of those lucky people who somehow managed to avoid ever contracting COVID. Maybe you are one of them. Is this a Marvel-like superpower? Is there any scientific reason why a person could be resistant to infection when the virus seems to be everywhere? Or is it just luck?

More than 60% of people in the UK have tested positive for COVID at least once. However, the number of people who actually contracted SARS-CoV-2, the virus that causes COVID-19, is estimated to be higher. The calculated rate of asymptomatic infections varies by study, although most agree it’s fairly common.

But even accounting for people who have had COVID and didn’t realize it, there’s probably still a group of people who never had it. The reason some people appear to be immune to COVID is a question that has been asked throughout the pandemic. As with so many things in science, there is not (yet) a simple answer.

We can probably dismiss the Marvel-like superpower theory. But science and luck both probably play a role. Let’s take a look.

The simplest explanation is that these people have never come into contact with the virus.

This could certainly apply to people who have been shielded during the pandemic. People at significantly higher risk of serious illnesses, such as People with chronic heart or lung disease, for example, have had a tough few years.

Many of them continue to take precautions to avoid possible exposure to the virus. Despite extra safety measures, many of these people have contracted COVID.

Due to the high level of transmission in the community, particularly in the extremely transmissible Omicron variants, it is very unlikely that someone going to work or school, socializing and shopping has not been in the vicinity of someone infected with the virus is infected. Still, there are people who have experienced high levels of exposure, such as B. Hospital workers or family members of people who have had COVID who somehow managed to avoid testing positive.

We know from several studies that vaccines can not only reduce the risk of serious illness, but also reduce the likelihood of SARS-CoV-2 transmission in the home by about half. The vaccination could certainly have helped some close contacts not to become infected. It’s important to note, however, that these studies predated Omicron. The data we have on the effect of vaccination on the transmission of Omicron is still limited.

Some theories

One theory as to why certain people have avoided infection is that despite being exposed to the virus, they can’t detect infection even after it has entered the airways.

This could be due to a lack of receptors that SARS-CoV-2 needs to gain access to cells.

Once a person has become infected, researchers have found that differences in immune responses to SARS-CoV-2 play a role in determining symptom severity. It is possible that a rapid and robust immune response could prevent the virus from replicating at scale in the first place.

The effectiveness of our immune response to infection is largely determined by our age and genetics. However, a healthy lifestyle certainly helps. For example, we know that vitamin D deficiency can increase the risk of certain infections. Too little sleep can also have a detrimental effect on our body’s ability to fight off invading pathogens.

Scientists studying the underlying causes of severe COVID have identified a genetic cause in nearly 20% of critical cases. Just as genetics could be a determining factor in disease severity, our genetic makeup could also hold the key to resistance to SARS-CoV-2 infection.

I am researching SARS-CoV-2 infections on nasal cells from human donors. We grow these cells on plastic dishes, which we can then add virus to and see how the cells react. During our research, we found a donor whose cells could not be infected with SARS-CoV-2.

We’ve uncovered some really interesting genetic mutations, including several involved in the body’s immune response to infection, that might explain why. A mutation that we have identified in a gene involved in detecting the presence of a virus has previously been shown to confer resistance to HIV infection. Our research covers a small number of donors and shows that we are still only scratching the surface when it comes to research into genetic susceptibility or resistance to infection.

There is also the possibility that previous infection with other types of coronaviruses leads to cross-reactive immunity. At this point, our immune system can recognize SARS-CoV-2 as similar to a recently invaded virus and trigger an immune response. There are seven coronaviruses that infect humans: four that cause the common cold, and one each that causes Sars (Severe Acute Respiratory Syndrome), Mers (Middle East Respiratory Syndrome), and COVID.

How long that immunity lasts is another question. Seasonal coronaviruses that circulated before 2020 could reinfect the same people after 12 months.

If you’ve managed to avoid COVID so far, you might have natural immunity to SARS-CoV-2 infection, or maybe you’ve just been lucky. Either way, it makes sense to continue taking precautions against this virus we know so little about.

Lindsay Broadbent, Research Fellow, School of Medicine, Dentistry and Biomedical Sciences, Queen’s University Belfast

This article was republished by The Conversation under a Creative Commons license. Read the original article.