Washington (AFP)

The "messenger RNA" technology of the vaccines developed against Covid-19 by Pfizer / BioNTech and Moderna, which have each announced that they are very effective according to clinical trials, is recent and had never been proven .

The pandemic was a boon for the technique and its developers.

All vaccines have the same goal: to train our immune system to recognize the coronavirus, to raise its defenses in a preventive way, in order to neutralize the real virus if it were to infect us.

Conventional vaccines can be made from inactivated (polio, influenza), attenuated (measles, yellow fever) viruses, or just proteins called antigens (hepatitis B).

But in the case of Pfizer and its German partner BioNTech, as well as Moderna, we inject into the body strands of genetic instructions called messenger RNA, the molecule that tells our cells what 'we must manufacture.

Every cell is a mini-factory of proteins, according to the genetic instructions contained in the DNA of its nucleus (DNA is transcribed into RNA when needed).

The vaccine's messenger RNA is made in the laboratory.

He inserts and hacks this machinery to manufacture proteins or "antigens" specific to the coronavirus: its "spikes", these so recognizable points that adorn its surface and allow it to attach to human cells to penetrate them.

These proteins, harmless in themselves, will be released by our cells and delivered to the immune system, which will then produce antibodies.

These antibodies will remain, standing guard for, hopefully, a long time, able to recognize and neutralize the coronavirus if it were to infect us.

At no time is the SARS-CoV-2 virus, even inactivated, injected, and the RNA cannot integrate into our genome.

- Ultra-cold storage -

The advantage is that with this method, there is no need to cultivate a pathogen in the laboratory, it is the organism that does the work.

It is for this reason that these vaccines are faster to develop.

No need for cells or chicken eggs to generate this vaccine (unlike flu shots).

With RNA vaccines, "all you need is the sequence" of the antigen, told AFP David Weissman, an immunologist who co-invented a technique refined in the mid-2000s who paved the way for this technology.

He is now a consultant for BioNTech.

"RNA vaccines have the interesting feature of being able to be produced very easily in very large quantities", summarizes Daniel Floret, vice-president of the Technical Committee on Vaccinations, at the High Authority for Health.

The downside: the vaccine, wrapped in a protective lipid capsule, must be stored at very low temperature, because the RNA is fragile.

Pfizer's requires -70 ° C, a much lower temperature than standard freezers, and which has forced the group to develop specific containers, filled with dry ice, to ship the doses.

Moderna's is stored at -20 ° C, which will require the maintenance of the cold chain from the factory to the pharmacies.

DNA vaccines, on the other hand, can be stored at room temperature because DNA is very resistant.

To date, no DNA or RNA vaccine has been approved for humans.

DNA vaccines exist for veterinary use: horses, dogs, salmon ...

The Covid-19 has given technology a huge boost.

Moderna, a biotechnology company founded in 2010 that still has no authorized product, received $ 2.5 billion from the US government to develop the vaccine, and produce 100 million doses.

If the technology is proven, it could pave the way for other treatments.

BioNTech was founded in 2008 with the ambition, still current, to create tailor-made treatments against cancer, and Moderna has been developing vaccines against Zika, the Epstein-Barr virus (mononucleosis) and the respiratory virus for years. syncytial (bronchiolitis ...), cytomegalovirus (which can pose a risk to the fetus), or simply against the flu.

© 2020 AFP