The active ingredient: mRNA
Messenger RNA is a temporary copy of a DNA fragment of the virus’ S spike protein. During the injection, the cells will read the mRNA and synthesize the protein. This is what will trigger our body’s immune response. This messenger RNA cannot be integrated into our DNA, it is quickly eliminated once read.
Lipids
Lipids protect mRNA by enveloping it in a lipid nanoparticle, intended in particular to facilitate its penetration into the cell. Lipids give the liquid an off-white appearance.
Salt
Salt balances the pH so that it approximates the pH of the human body. It is used to prevent the vaccine from breaking down too quickly. The Pfizer-BioNtech vaccine contains four different salts: sodium chloride, potassium chloride, monobasic potassium phosphate and dibasic sodium phosphate dihydrate.
Sugar
The sucrose contained in the vaccine serves as a preservative to protect the nanoparticles during freezing and to prevent them from sticking together.
Some water
The water is used to bind the elements that go into the composition of the vaccine.
No adjuvant
Unlike inactivated virus or recombinant protein vaccines, RNA vaccines do not require adjuvants. The main adjuvant used by laboratories around the world is aluminum salt.
Why have there been cases of allergy?
Two people have had a severe allergic reaction to the injection of Pfizer’s vaccine in the UK, but it is not yet clear which of the ingredients is involved. The UK Regulatory Agency has currently advised people with a history of acute allergic attacks not to be vaccinated.