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How do the main vaccines work?

By videoconference from home, the correspondent of Science explains the mode of action of the main vaccines against Covid-19. And especially how they will allow the body to produce the antibodies that will prevent the virus from entering cells.

In this English-language video, Jon Cohen, the correspondent of the American scientific journal Science, explains how our immune system works and the different vaccines that should protect us from Covid-19.

He recalls that the laboratories have relied on eight distinct modes of action, also called “platforms”. “The vast majority focus on the ‘spike’ protein, the protein on the surface of the coronavirus”, he emphasizes. Because it is this protein that has the ability to attach to a receptor in our cells. Functioning like a key in a lock, the “spike” can in this way penetrate our cells and give the virus the opportunity to reproduce.

Thus, if antibodies block the access of the virus to our cells, “in theory”, insists the journalist, we prevent the infection. The vaccines, each in their own way, will trigger the complex response of the immune system and allow the creation of antibodies.

To do this, the Pfizer-BioNTech and Moderna laboratories use theARN messenger of viral protein, encapsulated in a lipid particle. For their part, AstraZeneca-Oxford, Johnson & Johnson, the Russian Gamaleya or the Chinese CanSino use a Trojan horse: it hides the gene for the “spike” protein in another harmless virus.

Others, like Novavax, use not the gene but the “spike” protein directly, without the original virus, which they add to an adjuvant to attract the attention of the immune system. As for the Sinovac, Sinopharm and Valneva laboratories, they use an “old” technique which consists in inoculating the deactivated virus. “But whatever the technique they together have the potential to create several lines of defense against Sars-CoV-2”, insists Science.

Jon Cohen notes that there has never been so much joint effort to understand how vaccines work. Not just in theory, but at the antibody level. It shows what understanding the details of our immune response could mean for the future of human trials.

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