05-05-2021 by Mirai
The Pfizer / BioNTech and Moderna anti-Covid serums have one thing in common: they are messenger RNA vaccines. Is this technology effective in combating Sars-CoV-2 variants?
The spread of Sars-CoV-2 variants around the world remains a concern as they are more contagious, but could also call into question the efficacy of vaccines.
If the vaccination campaign intensifies, the question of the efficacy of vaccines, and particularly those with messenger RNA, on these mutations continues to grow. And for good reason: Most of the first few doses were done with Pfizer / BioNTech serum.
Both Pfizers and Modernas serum have one thing in common: They are messenger RNA vaccines, a technology that aims to make the body produce fragments of infectious agents to trigger the immune response.
Messenger RNA Vaccines: Less Effective Against Brazilian and South African Variants?
Do these serums protect us against Sars-Cov-2 variants? A study in the journal Cell investigated the effectiveness of messenger RNA vaccines on coronavirus mutations. To do this, the researchers took the sera, that is, the liquid part of the blood, from 99 patients vaccinated after one and then two doses of the Pfizer / BioNTech and Moderna vaccine.
The authors of this work revealed that these messenger RNA vaccines provided good protection against the historical strain of Sars-CoV-2 and against the British variant. What about the other variants? "We found that the new strains first described in South Africa were 20 to 40 times more resistant to neutralization, and that the two strains first described in Brazil and Japan were five to seven times more resistant, compared to the original virus, "he said. Alejandro B. Balazs, an assistant professor of medicine at Harvard Medical School, an assistant researcher in the department of medicine at Massachusetts General Hospital in Boston, and a co-author of the study. When viruses are less sensitive to the immunity conferred by vaccination, this is called "vaccine escape."
These findings are in line with previous work done by the Pasteur Institute on the Pfizer / BioNTech vaccine. The results showed that one week after the second dose, the vaccine was 80% effective against the original strain of Sars-CoV-2 and the English variant. On the other hand, its effectiveness increased to 60% compared to the South African variant.
Pfizer and Moderna adapt their vaccines
Should we be concerned about the possible decrease in efficacy of messenger RNA vaccines when faced with the Brazilian and South African variants? In The Conversation, Anne Goffard, a virologist at the University Hospital of Lille, underlines the limits of the work published in the journal Cell: "This study, very rigorously carried out, is still an in vitro study; it does not allow conclusions to be drawn as to the clinical consequences of these results obtained in cultured cells ", he indicates.
Another aspect to take into account: vaccines based on this technology have a significant advantage, because they are faster to develop and, therefore, to modify. "There are formats that are faster and easier to adapt. Clearly, these are messenger RNAs," Sylvie Van der Werf, a virologist at the Pasteur Institute, explained to AFP last March.
Currently, the laboratories of Pfizer and BioNtech are testing the effectiveness of a third dose of their vaccine against mutations in the virus. For its part, Moderna notably assesses the need for specific drivers to provide better protection against the South African variant.
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