It all points to the fact that the worst of the Covid pandemic has passed in Spain, although the disease continues to cause hospitalizations and deaths. But it has been two long years that we have had to learn to live with this virus. And after this long time when more than 12 million infections were recorded in Spain, there are still people who have managed to avoid infection, or at least the disease caused by SARS-CoV-2. How did they achieve this?

How many people have survived Covid?
First of all, it should be noted that the number of recorded cases of Covid is not an adequate indicator to estimate how many people have survived the infection. The 12.24 million cases cited by statistics imply that 26% of the Hispanic population suffers from this disease, but this figure includes some people who have been infected several times, while ignoring many who have been infected and whose transmission has not been recorded in the statistics. . This includes many asymptomatic infections.

The last major serological study conducted by the authorities was carried out in December 2020, before the introduction of the disease vaccine, and it is estimated that around 10% of the population suffers from the infection.

More recent studies show the figure has grown over the past year and a half. The authors of a seroprevalence analysis in the Community of Valencia noted that their data (50%) could be estimated for the rest of Spain. The European Commission’s estimates show instead that the proportion of Europeans infected at some point will be higher, between 60% and 80%.

Asymptomatic cases or people who have never been infected.
This discrepancy between the numbers is due to the nature of the data, measuring different things, but also due to the fact that many people go through the infection without suffering from the symptoms of the disease. We all know someone who doesn’t suffer from Covid but has to get tested regularly, few can say they’re not infected.

We don’t know why.
However, we do know that there are people who are not infected, symptomatically or asymptomatically, although we do not know for sure how many there are. What we don’t know is why and how they managed to stay safe during this two-year pandemic. Queen’s University Belfast researcher Lindsay Broadbent recently attempted to answer this question in an article she wrote for The Conversation.

The first intuition is that these people were not exposed to the virus. It is true that many people have taken their precautions against the virus to the extreme, but these measures cannot explain the number of uninfected people. After the 26-month pandemic, many “let their guard down” without being infected later on.

Chance.
However, this explanation contradicts people’s experiences. There are cases where people are known to become infected without even knowing when, and there are cases of close contact without the infection.

There are an infinite number of factors that affect luck and that we can attribute to it: viral load, properties of the space surrounding us, air currents… That’s why there is so little we can be sure of.

Vaccines.
It is true that many people “let their guard down” after vaccination, and this can be an important factor. Again, vaccines may be only partially responsible for this phenomenon. Vaccines are known to have a high success rate in preventing serious cases of Covid, but they have less ability to limit infections.

However, Broadbent notes in his article again that vaccines cannot fully explain this phenomenon, as the introduction of omicron further reduces the ability of vaccines to prevent SARS-CoV-2 infection.

Any other explanations?
In Broadbent’s paper, the researcher points to other possible explanations. In it he talks about the possibility of the corresponding factor being in the receptors of cells. In this case, the virus will enter the body of these immune people, but will not be able to enter the cells to multiply and unleash a chain reaction.

University of Birmingham immunologist Zania Stamataki points to this possibility in an article for The Guardian. In it, she explains the possible role of the ACE2 proteins, which may help explain why children are less vulnerable to this disease.

Another possibility Broadbent considers has to do with the immune response. It is known that the response of this defense system has a lot to do with the symptoms of the disease, but its fast and effective action could, in theory, prevent the virus from spreading in the human body at its root.

But why only some people?
There are three factors to consider. The first of these should be about lifestyle, healthy habits should have some effect. The article cites sleep as an example, not getting enough sleep can condition the body’s ability to ward off infections.

The second thing to take into account, according to Broadbent, is less up to us, and that’s genetics. Genetics are known to be associated with the appearance of severe Covid symptoms. Therefore, it is plausible that genetics are behind these processes in which the body gains an upper hand against infection.

While it is useful to confront future outbreaks later on, efforts in this direction can be predicted to give us more clues about the interaction between genetics and vulnerability to Covid.

The third explanation can come from outside our body. About 200 types of coronavirus are known, but the variants known to affect humans do not reach 10. Four types of coronavirus are actually the cause of 30% of the common cold.

From the early stages of the pandemic, there was speculation that the common cold caused by these viruses could induce immunity against Covid. According to some experts, the key may lie in T lymphocytes, the key cells in the immune system responsible for protection against viruses and other organisms.

For Broadbent, this is a possibility, but he also points out that it contradicts the re-infection rate of Covid, which allows several infections within a year to be possible.

Both Stamataki and Broadbent conclude their papers with a cautionary tale, with the words “It makes sense to continue taking action against this virus, about which we know so little.”

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