This is how the Pfizer vaccine works, the first to arrive in Spain against the coronavirus

Publication: Sunday December 27 2020 08:46

Vaccines are already a reality in Spain and in the European Union. The one developed by Pfizer and BioNTech was the first to reach our territory, but do we know how it works?

On the day of the start of the vaccination campaign in Spain, we review the key aspects of this vaccine, BNT162b2. It bears the generic name of tozinameran and the brand name is Comirnaty, perhaps its most well-known designation.

Its main ingredient is mRNA, the molecule that carries the instructions for our body to produce the protein spike or coronavirus spike, the same protein it uses to get into our cells. The idea is that if the immune system is able to make antibodies that block it, it will not be able to enter our cells, multiply and cause disease.

This molecule is synthetic, made by scientists, and can overcome the body’s defenses and at the same time stimulate the immune system. However, it is very fragile and that is why it should be stored at extremely low temperatures, between 60 ° C and 80 ° C below zero.

These molecules must be stored in fatty spheres of a size similar to that of the coronavirus. The main lipid is ALC-0335 and this is because it is ionizable: a positive electric charge can be added to it. Since RNA is negatively charged, they stick together.

The other lipids, including the cholesterol molecule, are there to give structural integrity to the particles or prevent them from clumping together. It all mixes with RNA in a bubbly mixture that the FDA describes as a “white to off-white” frozen liquid.

Pfizer’s vaccine contains four salts that form phosphate buffered saline, PBS, which helps maintain the pH (acidity) of the vaccine at levels similar to those in a person’s body. In addition, the vaccine contains sugar, a natural antifreeze, which allows spherifications with RNA to freeze at these low temperatures.

The Pfizer / BioNTech vaccine requires two doses to work properly, two injections 21 days apart. Each vaccine vial contains five doses of 0.3 milliliters each and must be frozen before injection. The vaccine should be diluted with an exit solution and used within a maximum of six hours.

According to the World Health Organization, it should be effective for at least six months. To achieve overall immunity, it will be necessary to vaccinate 70% of the population.

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