July 25, 2021

robust and lasting post-infection immunity against Covid-19

Immunity to SARS-CoV-2 in most infected people lasts at least a year and may persist for several years. Better yet: after a single injection of the vaccine, these people seem to develop an extremely robust immunity, able to resist the new variants. This is demonstrated by publications devoted to the immune response to a natural Covid-19 infection, published in May in journals or in prepublication (before peer review). Very encouraging results, as many countries are taking advantage of the summer lull to accelerate the vaccination of their populations and try to regain control of the epidemic.

First of all, several studies show that the presence of antibodies persists in the body, while initial results showed a strong decrease after a few months. These proteins secreted by the body to identify and neutralize the virus are detectable in infected people up to thirteen months after encountering Covid-19, says the team of Samira Fafi-Kremer, director of the Institute of Virology de Strasbourg, which carried out a study on health personnel at the city’s CHU, published in preprint on May 15. Antibodies would be produced in number as long as the pathogen is present in the body, before rapidly decreasing within seven months of infection, finally stabilizing at a lower but constant level.

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“We knew that the antibody levels never stay very high in the blood, but since it is a respiratory virus and we do not generally follow their serology over time, no one dared to go too far on the subject, explains Samira Fafi-Kremer. There, we finally observe that the antibodies remain stable in a persistent manner and this is very good news. “ Indeed, if the body retained over the long term the levels of antibodies produced during its successive infections, the blood would quickly turn into a thick slurry.

“Memory” B lymphocytes

This kinetics of antibodies in two phases – decrease then stabilization – signals a transition between two types of cells secreting these proteins: plasmablasts, having a short life, give way “To a smaller but more persistent population of long-lived cells, generated later in the immune response”, write the researchers of the American team of Ali H. Ellebedy in a study published in the journal Nature le 24 mai.

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