How immunization works animation creator

Corona vaccination - This is how vaccination works

The corona vaccine from Biontech and Pfizer, as well as that from the newly licensed US manufacturer Moderna, is an mRNA vaccine. What is it actually and how does the vaccination work in the body? The immunologist Professor Michael Lohoff, head of the Institute for Medical Microbiology and Hospital Hygiene at the Philipps University, gives a picture-rich insight into our innermost being.

First of all, it should be said that the Covid-19 vaccines currently used in Germany do not have an effect due to weakened viruses, as with conventional agents. Instead, the messenger molecule mRNA (in German: ribonucleic acid, the “m” stands for “messenger”) acts as a kind of transporter that is “loaded” with information and delivers it to the immune system. To stay with this picture, the charge would be a “building instruction” for a component of the Covid-19 pathogen as a basis for stimulating the immune system.

A look inside our genetic information explains how the whole thing works in detail: The most important basis for the process is DNA or DNA (deoxyribonucleic acid), the genetic memory for the complete blueprint of a living being, human, animal, microorganism. The RNA in turn has various functions, it transfers this genetic information to the protein factories (“ribosomes”) and translates it there into proteins. Proteins ensure the functionality of the entire body; they consist of amino acids - a chemical compound - and are found in every cell.

The long DNA chains always consist of a double strand. This is doubled during cell division, and each daughter cell receives an identical copy. The information for the individual genes can be found on the DNA, each on a specific section. If a gene is to be produced as a protein, the corresponding section is "copied" - the mRNA is created.

The double strands are pulled apart in this section, "like a zipper with the corresponding points," explains Lohoff. There are four possible types of spikes (nucleotides), two of which can always pair in the zipper. The respective combination then determines which protein is formed and which “job” the cell takes on. From the muscle cell to the brain cell to the T cell (thymus cell) as part of the immune system.

The mRNAs for the various genes are created by the body again and again - as required - at the point in time when the “DNA zip” opens.

Vaccine provides "key construction"

The newly formed mRNA is initially in the cell nucleus, but leaves it and migrates to the “protein manufacturing factory” within the cell, Lohoff draws a graphic comparison. In doing so, it takes the information stored in the teeth with it as a "copy". The body uses this code to determine the proteins to be formed depending on the cell function. One of these possible functions is that of the "key". With its help, the cell can dock with other cells that have the appropriate “lock” protein on their surface.

Viruses also carry their own genes and with these they also carry one for their own “key”. They look for the right “lock” in the body - in the case of influenza they find it in the lungs. The virus infiltrates the cell and takes over the “factory” described above as a “Trojan horse”. It uses these to produce new virus DNA, RNA and proteins, thus spreading its damaging genetic material.

In order to find cells infected by viruses, the immune defense - consisting of antibodies and T cells - needs its own, modified "lock" - this differs from the one that the virus uses to dock on the cell, but it can still attack the intruder detect. And this is exactly where the vaccine comes in: it supplies the body with the mRNA that codes for the virus key and thus the “blueprint” that it can be built from.

The decisive factor here is that “a practically identical mRNA is produced during a natural infection, since the key is also formed there,” emphasizes Lohoff. In this respect, the vaccine only consists of a small part of the virus, "it only contains a subunit, which is less dangerous than if you were to take a whole virus".

As soon as the mRNA vaccine is injected into a person, the mRNA prepared in this way migrates to so-called phagocytes, where the information contained in the mRNA strand is copied and the antigen protein is produced in the “factory”. This is how the desired immune response is activated: the T cells armed with the right “key” are multiplied. They then help the B cells to produce suitable antibodies ("antiserum").

Professor Dr. Michael Lohoff. Source: Thorsten Richter

In the event of a real infection later on, these antibodies bind to the virus key and transport it to the phagocytes, which dispose of the whole thing. If cells are already infected, the T cells use their lock to recognize a fragment of the virus on the cell surface and kill the infected cell.

With a view to the widespread assumption among some vaccine critics that the vaccine interferes with the genetic blueprint of the body, the immunologist emphasizes: The genetic code transported by the mRNA is not incorporated into the human genome, “it does not even get there in the cell nucleus ". Just like in a one-way street, genetic information is exchanged with the body via the molecule in one direction - directly from the mRNA to the protein, bypassing the DNA.

A foreign gene, apart from the one for the virus key, is not involved. But that could also be a reason why the mRNA vaccination in the long term triggers a “not as massive” immune reaction as a vaccine that is based on a whole, albeit weakened virus. How long the immunity lasts, and therefore how often it has to be re-vaccinated, will have to be shown by studies.

Reaction to chemical components

Taken by itself, the actually "very labile" mRNA cannot survive at all, it has to be protected, which was an important part of the vaccine development: In the Biontech vaccine, the messenger molecule is therefore coated with lipids. These are fatty acids that are chemically produced, " this has been used for decades with certain medications, "says Lohoff. The body can also show temporary reactions to these chemicals. These are the side effects most commonly observed with a vaccination, such as redness or pain at the injection site.

The trigger, the chemical component, is then broken down in the body and disappears completely. “There are no long-term after-effects.” Theoretically, the immune system could inadvertently “mistake” its own protein for the key, which could possibly lead to an autoimmune reaction. But that is a theory and would be "the only realistic possibility" that problems could arise months later after a vaccination. Even in this theoretical case, he would still recommend a vaccination. "With a real virus infection, the key is there and the reaction could get much worse," emphasizes the microbiologist.

He wants to relieve other people's fear of the injection and urgently advises them to get vaccinated. Concern about the effects of a vaccine that has been tested and approved at an unprecedented pace, he understands "only partially - I trust the tolerance studies". As part of the previous vaccination, around 600,000 people who had been vaccinated had ten deaths - but they had died of previous illnesses, the cause of death could not be assigned to the vaccine, "nobody has died from the vaccination yet".

He warns against ignoring the virus, saying that SARS-CoV-2 - especially the more infectious variant - cannot be avoided: "You cannot avoid the virus, so either everyone will be infected at some point or they will be vaccinated", summarizes Lohoff. The vaccine is the drug of choice for him. Also against the mutations: According to previous knowledge, the vaccination is also effective against the mutation. "That was tested against 16 genetic variants and also helped there," says Lohoff. His conclusion: "We will not get past the vaccination - it can be controlled, with an infection you do not know how difficult it will be for the individual."

By Ina Tannert