Despite the successive waves of Covid-19 and other variants since 2020, we all know someone who has slipped through the cracks, someone who has never had it.
A study published in the journal Nature could explain why some people are immune to the coronavirus. In 2021, researchers carried out an experiment on 16 people who had never tested positive for Covid or been vaccinated. The original variant was injected into their noses, and then several nasal and blood samples were taken over the next 28 days.
Six people tested positive in the two daily tests carried out after injection for more than two days, while having symptoms. Three other people tested positive on only one of the two tests for up to two days, without showing symptoms. Finally, seven people have never tested positive for Covid.
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Scientists’ findings: in the second and third groups, patients secreted interferon (a substance that helps the immune system fight infections) directly into their blood, before it was produced in their nasopharynx, where nasal samples were collected. Nor was any infection observed in their T cells and macrophages (immune cells). Finally, according to the results, the subjects had high levels of activity of an immune system gene called “HLA-DQA2,” which helped prevent lasting infection.
Scientists hope this study can contribute to the development of a long-lasting vaccine and treatments. However, most people are exposed to “a true mosaic of variants of the virus, and not the only ancestral variant used in this study. It is therefore possible that the results do not reflect cellular responses outside of a testing context,” recognizes José Ordovas-Montanes of the Harvard Stem Cell Institute in Massachusetts (United States), a member of the study.
