“Victory!”, proclaim the American laboratories Pfizer and Moderna in concert. Both claim, by press releases, to have found the martingale to fight against Covid-19, with vaccines which would be effective respectively at 95% and 94.5%. It is also necessary that these results be published in scientific journals, verified by other researchers and, finally, approved by the health authorities of possible buyer countries, starting, across the Atlantic, by the Food and Drug Administration (FDA , which grants the authorization to market vaccines and drugs in the United States).
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Completely new, the two vaccines in question are based on messenger RNA, a coded sequence that sends instructions against the virus. What is it about ? What are the differences with vaccines created against other more “classic” viruses? We take a look back at this technology which had never before been authorized for use in human health.
What is it about ?
“While the traditional technique of vaccines consists of injecting an inactivated (or attenuated) virus so that the body learns to defend itself against it, the messenger RNA technique consists of sending a message to the body under the shape of a piece of DNA. Its purpose is to encourage the body to manufacture itself an inactive fraction of the virus, then the antibodies to fight against this virus “, summarizes the magazine “Further investigation” in the video below.
More precisely, RNA is a store of information, the equivalent of a recipe, which then makes it possible to generate a protein. “RNA (ribonucleic acid) transcribes the genetic information of part of the virus “, explains Etienne Simon-Lorière, head of the RNA virus evolutionary genomics unit at the Institut Pasteur, contacted by franceinfo. This RNA thus forms a code giving instructions which allow living cells to generate a protein “.
The RNA vaccine against Covid-19, continues this specialist, “is therefore a fragment of RNA that generates the protein placed on the surface of the virus. If the vaccine is effective, the body will learn to recognize this external protein, which is called the spicule of Sars-CoV-2, and it will generate immune responses, in the form of antibodies and cellular response “.
What is the difference with a conventional vaccine?
This ultra-innovative technology is a radical break with conventional vaccines. These consist of injecting the virus into the body, either in an attenuated form or in an inactivated form, to provoke an immune response. “Attenuated virus vaccines include those against yellow fever or measles”, explains Etienne Simon-Lorière. “The virus then infects our cells without making us sick, which makes it detected by the immune system, which produces its defenses”.
“As for inactivated viruses, he continues, they consist of growing the virus and then rendering it inactive with heat, for example, or with chemical treatment. A Chinese company (Sinovac Life Sciences) has thus developed a vaccine candidate against Covid-19 in this inactivated form “.
What is the advantage of this technology?
Compared to conventional vaccines, the advantage lies in particular in the mode of development. “It can go very quickly as soon as we know the sequence of a new virus that emerges”, explains Etienne Simon-Lorière.
“You can synthesize in a few weeks a piece of DNA that serves as a template for the RNA vaccine. Then it’s like making a journal: once you’ve produced the template, you can easily photocopy it from anywhere. billions of copies. “Etienne Simon-Lorière (Institut Pasteur)
“There is no need, as is the case with inactivated vaccines, to manufacture large quantities of virus in the lab, which is not easily done on a large scale “, he develops. The conservation of this vaccine, it remains subject to caution: that of Pfizer, for example, requires a temperature of -70 degrees, which is beyond the reach of conventional pharmacies. Moderna’s can be kept up to 30 days at a temperature of two to eight degrees, according to the lab release.
Should we fear RNA vaccines?
Fears are already appearing about this technology based on genetic information, hitherto unauthorized on humans. In an interview with the Swiss Radio and Television (RTS, the French-speaking public channel), the boss of Moderna, Stéphane Bancel, wanted to reassure the worried. “Messenger RNA technology is very interesting (…). It does not touch the nucleus of the cell, which is very important not to take risks with your DNA “.
Etienne Simon-Lorière confirms: “The genetic material of the vaccinated person, which is in the nucleus of the cell, will not interact with the RNA of the vaccine. This technology has also been studied for years. Before the pandemic, there were already several messenger RNA vaccine candidates under development by several groups. But other questions remain, and in particular this one: the duration of effectiveness of RNA vaccines is not known. Immunity could disappear more quickly than with other vaccines, we have no hindsight on this technology “.