Viruses in the fight against a virus – how does a vaccine work?

Few things in medicine, if any, have saved as many lives as vaccines. Smallpox, polio, diphtheria, tetanus, measles, whooping cough, mumps and rubella. All of these diseases are basically just a memory. At least if you have the advantage of growing up in Sweden or another welfare state.

Admittedly, no one believes the virus that causes covid-19 sars-cov can be eliminated with the help of vaccines, but for the individual – and thus society as well – it means protection. The clearest evidence of this is the sharp decline in the number of Swedes who die every day from Covid-19, despite the fact that the spread of infection has risen and is now at one of the highest levels since the epidemic began just over a year. Ago.

But what do the different vaccines contain and how do they work?

The European Medicines Agency (EMA) has so far approved four different vaccines, although we in Sweden have so far chosen not to start using them from the pharmaceutical company Janssen. Additionally, there is also a recommendation that the Astra Zeneca vaccine should only be given to people 65 years of age or older.

Two different principles

Regardless, these vaccines work on two different principles. There are so-called mRNA vaccines and so-called vector vaccines.

Modern and Pfizer-Biontech vaccines against covid-19 are called mRNA vaccines. MRNA stands for ‘messenger ribonucleic acid’ or messenger RNA in Swedish.

RNA is the molecule that forms when a cell mechanism reads genes in the genome and makes a protein. Before the RNA molecule becomes a protein, it is cut apart and becomes mRNA, which then emerges from the cell nucleus where it is used as a template for protein formation. Thus it is a messenger for the information contained in the genome (DNA), hence the name. Every day and every second, billions of tiny bits of messenger RNA are formed from all the genes that you read inside our cells, which in many ways function as tiny protein factories.

Flesh deceives

Each dose of Modern and Pfizer-Biontech vaccines contains large amounts of these small pieces of mRNA. But the code in these pieces does not consist of instructions for making a protein for the body, but rather of a code for the nail protein of the virus, which the virus uses to enter the host cell. In this way, the body is tricked into producing a small piece of the virus, which the body’s immune system reacts to and forms antibodies against it.

The Janssens and Astra Zenecas vaccines are called vector-based vaccines. These vaccines are based on DNA rather than RNA. This, in turn, means that the genetic code in these vaccines must reach the cell’s nucleus for it to be read. To do this, you get help from another virus, an adenovirus that has been modified to carry instructions for the nail protein. The virus enters the cells and attaches itself to the nucleus of the cell and injects its contents, that is, the genetic code for the nail protein, which the cell then reads and forms a protein from it, with which the body then interacts with it. Thus, adenovirus acts only as a “vector” or vector.

Risks and benefits

There are pros and cons to both approaches. For example, mRNA vaccines can be manufactured in large quantities in a short time. On the other hand, these vaccines are sensitive. RNA degrades easily, so it must be “packed” into small lipid molecules of the messenger RNA found in these vaccines. However, vaccines are sensitive to shocks. In addition, it should be stored really cold, which is not necessary for Janssen and Astra Zeneca vaccines, as the DNA is more stable.

The recent discussion of side effects and skepticism touched on vector-based vaccines, as a link was discovered between these vaccines and an unusual type of coagulation disorder meaning that a small number of patients who took these vaccines had experienced an unusual condition. The type of blood clot in the brain, plus a low platelet count, which can cause bleeding. The condition is serious but very rare. Researchers do not yet know why these vaccines might, in rare cases, cause this side effect. However, the overall assessment is that the benefits of the Astra Zeneca vaccine far outweigh the risks.