It’s the burning question on everyone’s mind. How did I get Covid twice despite being fully vaccinated? How has my next-door neighbor, who has been quarantined with her infected children for the past month, managed to escape contracting the virus?

Why do some people become infected with coronavirus over and again, while others remain immune? Is it luck, genes, or something else?

In order to provide answers to all of these issues, a team of researchers from the United Kingdom and Brazil is investigating if certain people may have a natural immunity to the virus.

Their immune systems, it is thought, knew how to resist the virus even before the outbreak started. This fortunate few, if their blood and cells are carefully analyzed, may be able to provide scientists with critical insights into the nature of immune response.

They may also contain the secret to pandemic research’s holy grail: a universal Covid vaccine capable of eliminating any strain.

We have a tendency to think of immunity as something that is either present or absent — either we are immune to a virus or we are not.

But, as Danny Altmann, professor of medicine and immunology at Imperial College London, points out, this masks a plethora of difficulties. According to him, the genes that control our immunity are among the most diverse found in the human body, with significant variations from person to person.

When it comes to something as simple as your blood type, he points out that “there’s a very limited chequerboard” of gene combinations available. On the other hand, when it comes to immunity, ” I’m talking about thousands of possibilities on your chequerboard; no two people will ever look the same.”

Therefore, it should come as no surprise that some people are more susceptible to getting viruses than others. It’s possible to watch this unfold in real time in the laboratory.

Currently, researchers at Oxford University and Imperial College London are conducting “challenge studies,” in which individuals are purposely exposed to Covid and held in isolation for two weeks.

In this study, all volunteers have had the same number of vaccines. They also get the same amount of Sars-Cov-2 (the virus that causes Covid), in the same way, every time. Despite this, if the current challenge study is anything like past ones, scientists predict participants to mount very diverse immune responses. Some people will notice an increase in the activity of their antibody and T-cells, while others will not.

This can also be observed in the context of hospitals. At the start of the pandemic, researchers at University College London recruited a large cohort of London-based healthcare workers for their COVIDSortium study, which was funded by the Wellcome Trust. All of the volunteers were most likely exposed to Sars-Cov-2 while working in their respective fields. Their test results were closely checked at all times. At the conclusion of the study, approximately 20% of the healthcare workers displayed evidence of a clear-cut Covid infection, whereas the remaining 65% had clearly not been infected with the virus.

The remaining 15%, on the other hand, was the most intriguing. Individuals who fell into this third category looked to have had low-level “abortive infections,” which were not detected by PCR tests. They did not have antibodies against Covid in their blood, but they did have a significantly greater T-cell count than the general population, with particularly high levels of a specific T-cell known to combat Covid in their blood. They had effectively stopped the virus in its tracks before it had a chance to establish a base of operations inside their bodies. Despite the fact that the pandemic was still in its early stages, it appeared as though their immune systems had already learned how to combat Covid virus.

“They didn’t completely resist the infection, but they eliminated it so rapidly that it couldn’t be picked up by the standard test,” adds Mala Maini, co-author of the study.

Here was clear evidence that some people may be naturally immune to Covid. Prof Altmann, who was not involved in the study, says the results look “convincing”.

The findings presented here clearly demonstrated that some individuals may be innately immune to Covid. Prof Altmann, who was not involved in the study, believes the findings are “convincing.”

But what is the source of this innate immunity? The most plausible explanation is that these people’s immune systems have already been exposed to comparable viruses years or decades before, when they were exposed to other viruses. Sars-Cov-2 is a member of the human coronavirus family, which includes seven viruses, the majority of which are responsible for the common cold. All of these viruses have a very similar appearance. It is believed that as your T-cells learn how to fight one infection, they will get better at fighting them all.

Another, less well-researched possibility is that our genes are at blame. Many viruses are contagious, and scientists believe that some people may just be born immune to them. This issue was raised in 2008 when virologists in Kenya discovered a group of sex workers who had never contracted HIV despite having had unprotected relations with a large number of positive cases of the virus. It turns out that their cells lacked a critical receptor – the same receptor that HIV particles utilize to enter our cells and replicate themselves.

“Big studies are going on now to see if something similar might be happening in some people with Covid, but there’s no clear evidence for that yet,” adds Prof Maini.

Indeed, researchers at the University of So Paulo are currently recruiting 100 cohabiting couples for a study. In each case, one half of the marriage tested positive for symptomatic Covid, whereas the other half remained Covid-free throughout the investigation (with blood tests confirming they had no Covid-specific antibodies). The DNA of all 200 participants will be analyzed in order to look for genetic variances.

It will be fantastic news for them if it turns out that some people are naturally immune to Covid. However, it may also benefit the rest of us by expediting the creation of a pan-coronavirus vaccine that is capable of combating any strain. The newest generation of Covid vaccines has been developed to specifically target the spike protein, which is found on the virus’s outer edge, rather than the virus itself. The spike protein, on the other hand, changes often when the virus mutates. As a result, vaccines become marginally less effective with each new variant introduced.

Natural immunity, on the other hand, appears to act in a different way. Scientists at the University College London (UCL) study examined the blood of volunteers who appeared to have pre-existing immunity to the virus. Rather than the spike protein, their T cells were attacking proteins in the virus’s core. These proteins have a considerably lower likelihood of changing from one mutation to the next. Rather of being exclusive to Sars-Cov-2, they are commonly present in a wide range of coronaviruses. In the event that a vaccine could be developed to specifically target these inner proteins, it may be possible to defeat all coronavirus strains.

Experts emphasize that the science is still in its early stages. Prof Altmann believes that no one should “go around feeling Teflon-coated in some way.”

Nonetheless, as we reach the third year of the pandemic, it is unquestionably a positive indication.

Image Credit: Getty

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