Each of us should know one of the lucky people who somehow managed to avoid coronavirus infection. Is there any scientific reason why a person might be resistant to infection when the virus is ubiquitous? Or is it just luck?
The number of people actually infected with SARS-CoV-2 is believed to be significantly higher than the rates at which covid has been laboratory confirmed. The estimated frequency of asymptomatic infections varies by study, but most experts agree that it is quite common.
But even considering the people who had covid and did not realize it, there is still a possibility that there is a group of people who have never lived.
Why some people seem immune to COVID is one of the questions that persists throughout the pandemic. As with many things in science, there is no simple answer yet.
The simplest explanation is that these people have never been exposed to the virus. This could certainly be true for people wearing protective equipment during the pandemic.
However, due to the high prevalence of the virus in the community, especially with highly contagious omicron variants, it is unlikely that someone going to work, school, or shopping will not be near an infected person. However, even among healthcare professionals, there are those who somehow manage to avoid a positive test result.
We know from several studies that vaccines can not only reduce the risk of serious illness, but also reduce the chance of transmission of SARS-CoV-2 by about half. So definitely vaccination can help some people avoid infection. However, it is important to note that these studies were carried out before the emergence of omycron. Available data on the effect of vaccine on omicron transmission are still limited.
One theory that explains why some people avoid infection is that, despite exposure to the virus, they cannot become infected even after the virus has entered the respiratory tract. This may be because SARS-CoV-2 lacks the receptors it needs to access cells.
Researchers have found that when a person is infected, differences in the immune response to SARS-CoV-2 play a large role in how severe the disease will be. In some people, it is possible that a rapid and strong immune response can greatly inhibit the replication of the virus.
The effectiveness of our immune response to infection is largely determined by our age and genetics. However, a healthy lifestyle definitely helps. For example, vitamin D deficiency is known to increase the risk of certain infections. Lack of sleep can also harm our body’s ability to fight invading pathogens. Scientists investigating the underlying causes of severe COVID have identified a genetic cause in almost 20% of critical cases. While genetics may be one of the determinants of disease severity, it may also confer resistance to SARS-CoV-2.
There is also the possibility that previous infection with other types of coronavirus could lead to cross immunity. Therefore, the immune system can recognize SARS-CoV-2 as the counterpart of a new invading virus and trigger a timely immune response.
Another question is how long this immunity can last. Seasonal coronaviruses circulating until 2020 can re-infect the same people 12 months later.
If you’ve managed to avoid COVID so far, you may have a natural immunity to SARS-CoV-2 infection or just be lucky. In any case, it would be wise to continue taking precautions against this virus, about which we know so little.