We all know some of those lucky people who have somehow managed to avoid contracting covid. Maybe you are one of them.
Is it due to a superpower like that of the Marvel characters? Is there any scientific reason why a person might 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 actually infected with SARS-CoV-2, the virus that causes covid-19, is thought to be larger.
The estimated rate of asymptomatic infections varies by study, although most agree that it is quite common.
But even accounting for people who have had covid and didn’t realize it, there is still likely to be a group of people who have never been infected.
Why some people seem immune to covid is a question that has persisted throughout the pandemic. As with so much in science, there is no easy answer (yet).
We can probably rule out the Marvel superpower theory. But science and luck likely play a role. We’ll see.
The simplest explanation is that these people have never been in contact with the virus.
This could certainly be the case for people who have been protecting themselves during the pandemic.
People at significantly higher risk of serious illness, such as those with chronic heart or lung conditions, have had a rough two years.
Many of them continue to take precautions to avoid possible exposure to the virus. Even with added security measures, many of these people ended up with covid.
Due to the high level of community transmission, particularly with the extremely transmissible omicron variants, it is very unlikely that someone going to work or school, socializing and shopping have not been around someone infected with the virus.
However, there are people who have experienced high levels of exposure, such as hospital workers or family members of people who had covid, who somehow have managed to avoid testing positive.
We know from several studies that vaccines not only reduce the risk of serious illness, but also can cut in half the possibility of domestic transmission of SARS-CoV-2.
So certainly vaccination could have helped some close contacts avoid becoming infected.
However, it is important to note that these studies were done before omicron. The data we have on the effect of vaccination on omicron transmission are still limited.
One theory about why certain people have avoided infection is that, although they are exposed to the virus, it fails to establish an infection even after entering the respiratory tract.
This could be due to a lack of the receptors necessary for SARS-CoV-2 to access cells.
Once a person is infected, researchers have identified that differences in the immune response to SARS-CoV-2 play a role in determining severity of the symptoms.
It is possible that a rapid and robust immune response could prevent the virus from replicating in large numbers in the first place.
The effectiveness of our immune response to infection is largely defined by our age and genetics.
That said, a healthy lifestyle certainly helps. For example, we know that vitamin D deficiency can increase the risk of certain infections.
Not getting enough 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 almost 20% of critical cases.
Just as genetics could be a determining factor in the severity of the disease, our genetic makeup it may also be the key to resistance to SARS-CoV-2 infection.
I investigate SARS-CoV-2 infection in nasal cells from human donors. We grow these cells on plastic plates to which we can then add viruses and investigate how the cells respond.
During our investigation, we found a donor whose cells could not be infected with SARS-CoV-2.
we discovered some really interesting genetic mutations, including several related to the body’s immune response to infection, which could explain why.
A mutation we identified in a gene related to detecting the presence of a virus has previously been shown to confer resistance to HIV infection.
Our research is based on a small number of donors and shows that we are still scratching the surface of research on genetic susceptibility or resistance to infection.
There is also the possibility that a previous infection with other types of coronavirus result in cross-reactive immunity.
This is where our immune system can recognize SARS-CoV-2 as similar to a recent invading virus and launch an immune response.
There are seven coronaviruses that infect humans: four that cause the common cold and one that causes Sars (severe acute respiratory syndrome), Mers (Middle East respiratory syndrome), and covid.
The duration of this immunity is another question. The seasonal coronaviruses that circulated before 2020 they were able to reinfect the same people after 12 months.
If you have managed to avoid covid to date, you may have natural immunity to SARS-CoV-2 infection, or you may have just been lucky.
Either way, it is sensible to continue to take precautions against this virus that we still know so little about.
*Lindsay Broadbent is a Research Fellow at Queen’s University School of Medicine, Dentistry and Biomedical Sciences, Belfast, Northern Ireland. this artArticle appeared on The Conversation. You can read the original version here.
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