How the Pfizer vaccine works. It is based on a messenger RNA technology that has never been tested: Coronavirus

Among the four main categories of vaccines developed against Covid-19, the one used by Pfizer, which announced Monday that its vaccine is 90% effective, is based on a new technology called messenger RNA, according to AFP.

All vaccines have the same objective: to teach our immune system to recognize the coronavirus, to defend it in a preventive way, to neutralize the real virus if it infects us.

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

But in the case of Pfizer and its German partner BioNTech, or Moderna, which uses the same technique but has yet to announce any results, strings of genetic instructions called messenger RNA, the molecule that tells our cells what to do, are injected into the body. do. . Each cell is a mini-factory of proteins, according to the genetic instructions contained in its nucleus.

The messenger RNA of the vaccine is introduced and takes control of this machine to produce a specific antigen of the coronavirus: the “thorn” of the coronavirus, its well-known tip, which is found on its surface and allows it to adhere to human cells to penetrate.

This spike, harmless in itself, will then be detected by the immune system which will produce antibodies, and these antibodies will remain on guard, hopefully, for a long time.

Once the genetic material is injected, “the cells at the injection site will begin to temporarily produce one of the virus’s proteins, in this case protein S, the spike protein,” Christophe D told AFP . Enfert, scientific director of the Pasteur Institute.

Benefits

The advantage is that, with this method, it is not necessary to cultivate a pathogen in the laboratory, the body does the work. For this reason, these vaccines are growing faster. Chicken cells and eggs (as in the case of influenza vaccines) are not needed to make this vaccine.

“RNA vaccines have the interesting characteristic of being able to be produced very easily in very large quantities”, summarizes Daniel Floret, vice president of the Technical Committee for Vaccines

Note that it is not possible for RNA to integrate into a human genome, made up of DNA. “RNA, in order to integrate into the genome, must be transcribed in the opposite direction (in DNA), a procedure called reverse transcription, and this is not done spontaneously in cells,” explains Christophe D’Enfert.

As for the coronavirus protein, “it will not be produced all the time, it will stop” because, as with any vaccine, the immune system will destroy the cells that produce the viral protein. “Therefore, the process will end by itself”, explains Bruno Pitard (Inserm / University of Nantes), at the head of a start-up that works on this type of vaccine.

Disadvantages and applications for the future

The disadvantage of the latter: they must be stored at very low temperatures. The United States government has been implementing the necessary logistics for several months.

However, this is not mandatory for DNA vaccines, which can be stored at room temperature.

To date, no DNA or RNA vaccine has been approved for humans. On the other hand, there are DNA vaccines for veterinary use: horses, dogs, salmon …

Covid-19 has given a great boost to its production, especially due to public funding.

The US government, prompted by President Donald Trump, signed a $ 1.95 billion contract with Pfizer to administer 100 million doses if the vaccine is ever approved.

Moderna, the smallest US biotech company, in turn received a $ 2.5 billion grant to develop the vaccine and produce 100 million doses.

All of these doses will be shipped to the United States, which hopes to begin immunizing vulnerable people before the end of the year.

If the technology were tested, this could pave the way for many other vaccines: Moderna has been developing messenger RNA vaccines against Zika, influenza, Epstein-Barr virus (mononucleosis), respiratory syncytial virus (bronchiolitis … ) and cytomegalovirus for years. (often not serious, but can pose a risk to the fetus), but also against cancer.