“I never got Covid.” We are less and less numerous to pronounce this phrase. However, some continue to resist. So how do you explain, after seven waves, that some have never contracted Sars-CoV-2? The point with Sandrine Sarrazin, Inserm researcher at the Marseille-Luminy Center for Immunology.
To be or not to be contaminated… Since the spring of 2020, more than 32 million cases of Covid-19 have been identified in France. A figure that only reflects a part of reality. For Sandrine Sarrazin, Inserm researcher at the Marseille-Luminy Center for Immunology, “andAmong asymptomatic forms that have gone unnoticed, people who have been infected twice“Not to mention the screening campaigns that began long after the first cases occurred and the self-tests without counting, it is still difficult today to know for sure the number of people who have actually been affected by Sars-CoV-2.
Still, some have never developed the disease in 7 successive waves. So how to explain it?
- Isolated people or who had it without knowing it?
“It is difficult to imagine people who would not have been in contact with the virus“, notes Sandrine Sarrazin. “But there must still be rare cases of very isolated people, outside the big cities, who never take public transport, scrupulously respect barrier gestures, who may have escaped the virus… But this is probably not the majority of those who they never developed the disease. .“Another Hypothesis”those who had it but showed no symptoms, or who thought it was a cold or flu “, and therefore they imagine they have escaped through the cracks.
- A genetic predisposition?
“A French team (Inserm/APHP) led by Professor Jean-Laurent Casanova has already shown that genetic and immunological predispositions explain about 25% of severe forms of Covid-19, without necessarily having comorbidities. “, continues the immunologist. “On the contrary, there is no doubt that there are more genetically endowed people. The same team is also looking at the genes of health professionals exposed to Sars-CoV-2 before vaccines or masks were available… and who did not develop the disease..”
Other work has already been done on this possible “genetic protection”. Take, for example, these scientists from theUniversity of Newcastle who discovered that the HLA-DRB1*04:01 gene is found three times more often in asymptomatic people. This suggests that carriers of this gene exhibit some level of protection. Note, however, that this gene is directly related to latitude and longitude. Clearly, there are more carriers in Northern and Western Europe. This suggests that European populations are more likely to remain asymptomatic… while at risk of transmitting the disease to more susceptible populations.
- cross immunity?
A recent study published in the journal Nature Communications showed that being exposed to rhinovirus, the most common cause of the common cold, could protect against Sars-CoV-2 infection. In this work, researchers from theImperial College London found that the high levels of T cells generated by the body when infected with other human coronaviruses (such as the common cold), may protect against Covid-19 infection. “But this is just a hypothesis”, template Sandrine Sarrazin. “Vaccination also generates strong immunity. However, this does not prevent the disease from developing.“
- The blood group?
Since the start of the pandemic, scientists have been interested in the link between blood type and the risk of developing the coronavirus. Thus, many scientific publications have pointed out an association between belonging to group O and being protected against the Sars-CoV-2 virus. But Sandrine Sarrazin acknowledges that “we returned from this postulate. Because if there has been a correlation in studies between blood group and the severity of Covid cases, there has never been any demonstration of any protection against infection.
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