Pfizer vaccine: how does a messenger RNA vaccine work?

Will the wait for an effective vaccine against Covid-19 soon come to an end? Monday, November 9, the American pharmaceutical company Pfizer and its German partner BioNTech announced that they had developed a vaccine against Covid-19 which would be 90% effective. To achieve this high rate, the two pharmaceutical groups claim to rely on messenger RNA to tell our cells how to fight the coronavirus.

Messenger RNA, one of the conductors of our cells

Messenger ribonucleic acid, or messenger RNA, is a temporary copy of a section of our DNA, the genetic code for all our cells. A strand of messenger RNA contains all of the assembly instructions for a cell to create a protein. In the case of the vaccine proposed by Pfizer and BioNTech, the messenger RNA which will be injected into the body will have the mission of indicating to the cells which proteins they must synthesize to defend themselves against the coronavirus.

On their outer layers, coronaviruses are bristling with small spikes, called spicules, which are arranged in a crown-like shape, hence the name of the virus (coronavirus is the Latin word for crown viruses). These spikes, made up of glycoproteins, serve as a key to enter infected cells.

Normally, when the body encounters a viral or bacterial threat, it defends itself with antibodies produced by our immune system. Faced with the wide variety of attacks that the body can undergo, our organism needs a protein coming from the external threat to be able to identify it: this is the antigen. Once this antigen is in our possession, the immune system develops specific antibodies to effectively block the attack.

The idea of ​​the vaccine currently being developed is to help cells locate spikes of the coronavirus. Thanks to the messenger RNA that will be injected, the immune system will be in possession of a Covid-19 antigen, which will give it the possibility of producing the right antibodies, in order to ward off the infection.

Availability still uncertain

The method used by Pfizer and BioNTech has the advantage of being fast, since it is the organism itself that will create the right defenses, instead of waiting for them to be grown in the laboratory. But if the effectiveness of this vaccine reaches 90%, this does not necessarily mean that it will be available in the next few weeks. Phase III of the vaccine is underway and it is still too early to determine how long the injection will immunize our body against Covid-19.

In the current state of things – assuming that this new remedy goes through clinical trials and that it is validated by the health authorities – the vaccine would be available at the end of the year in the best case, but more likely early next year, and in limited stocks. The European Union and the United States are in the running to have access to this vaccine first. It would be administered as a priority to health personnel, who are on the front line to curb the pandemic, as well as to the elderly and vulnerable, the most affected by the severe forms of Covid-19.