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How does a vaccination work?

Our immune system

Even in today's clean environment, the human body is exposed to a large number of different pathogens. These can be bacteria, viruses or even fungi and enter the organism through so-called entry ports (such as the gastrointestinal tract, the skin or the urogenital tract). In healthy people, they are faced with a multitude of different cells that all pursue the same goal: the immune defence. These cells are therefore also called defence cells (or immune cells). If a pathogen enters the organism for the first time (infection), the immune cells do not yet know it and the fight against the pathogen is energy- and time-consuming. There is a special form of the defence cell that remembers certain building blocks of the pathogen. Therefore, this cell is also called memory cell. In addition, the body produces specific antibodies against the pathogen. Antibodies are a kind of "weapon" that helps the body to combat the pathogen in future infections. After the initial infection, the body is therefore prepared for the disease on the basis of memory cells and antibodies against the pathogen. If the attacker makes it back into the body (second infection), the immune defence is stronger, faster and costs less energy. This is also the reason why you only have to go through many (not all) children's diseases once.

This body's defensive behavior is comparable to a group of villains who all have long noses and want to invade the city. During the first attack, the police do not yet know the villains, so it takes longer and more energy to defeat them. In a second fight, however, certain "memory policemen" recognize the long noses of the villains and can sound the alarm so that they can start a specific and quick defensive action more quickly and easily.

Active immunisation (vaccination)

Active immunisation is based on the principle of the immune system described above. One wants to prepare the body for a certain pathogen, so that one is prepared for the event of a real attack and can easily and quickly defeat the disease. Nowadays, of course, one does not take any real attackers and vaccinate them in humans, since many of the pathogens that are vaccinated against are very dangerous or complex. Instead, we use attenuated, dead or even only certain parts of the pathogens (such as the surface structures of the attackers) and inject them into the body. The latter then thinks that he is actually attacked and starts an immune reaction (defense). During this immune reaction, it forms memory cells and antibodies against the vaccinated pathogens. If, after a vaccination, the body is prepared for an attack by the real pathogen, the body is prepared and can even start a rapid and strong immune defence against very bad diseases.

Live and dead vaccines

In vaccination, the body should be prepared for certain pathogens. However, in order not to expose the body to any real disease (dangerous and complicating), one does not vaccinate the real pathogen. A distinction is made between strongly attenuated pathogens which are unable to cause a disease and killed pathogens. The third option is to inoculate only specific, typical components of the pathogen that are produced by genetic engineering.

So if you want to prepare the city for a certain group of villains with long noses, you can either let a very weak attacker (live vaccination) or a dead attacker (toxic vaccination) into the city, who both have long noses but can't do any damage. As a third possibility, you can also simply show long noses (which you have to make artificially) to the policemen, so that they can remember the "evildoer sign" long noses. If the long nose villains actually attack later on, the police know about it and are able to fend off the attack.

Combination vaccines

The immune response of the vaccination is always only specific to a pathogen, i. e. if I have myself vaccinated against mumps, I am immune to mumps, but not for measles. However, there are vaccinations in which you not only get the vaccine against one disease, but also against several, e. g. the mumps-mass-grass rubella vaccination. These vaccinations have the advantage that you will only be paged once (less pain, fewer visits to the doctor), the vaccination is cheaper and you have to take up fewer additives in the body. The immune response is tolerable even for small children without problems.

Thus it can be useful that one can warn the policemen of a city not only against long nose offenders, but at the same time also against big-eared gangsters.

Risks and side effects of vaccinations

Those who are a little concerned with the literature on the risks of vaccinations are quickly confronted with the statement "vaccinating causes autism". This claim is based on a publication by an English physician (and vaccination opponent) who claimed that the mercury (then) contained in vaccinations could cause mental illness in children. As a result, mercury was banned from all the usual vaccines, and a large number of researchers tried to prove the results of the English physician - without success. A few years later, it turned out that the results of the study were falsified with the aim of suing large pharmaceutical companies for damages. The doctor in question has lost his profession and had to emigrate to the USA. Large-scale studies1 show that there is no link between vaccinations and autism.

Nevertheless, it is important to be aware that vaccinations carry side effects and risks, but these are extremely rare. The most frequent side effect is a so-called vaccination reaction, i. e. a visible reaction of the body to the vaccine. These include redness, swelling, pain, fatigue, but also flu-like symptoms. The frequency is quantified at up to 1:100. Vaccination complications, i. e. a disease that goes beyond the usual extent of an inoculation reaction (e. g. febrile cramp) and is listed with up to 1:1000, are significantly less common. Vaccination damage, i. e. permanent damage after vaccination or a complication of vaccination (1:1,000,000) is very rare. Once again, the so-called vaccination disease is much rarer (and cannot be summed up in figures). This can be done by vaccinating with a weakened live vaccine and then returning the attenuated pathogens to a stronger normal form of the pathogen. Then it is possible that the actual disease occurs in a weakened course (e. g. vaccine measles). Such a disease is extremely rare.

In our example, it can happen in rare cases that one of the long-nosed wrongdoers, who is weakened or even dead, actually causes damage in the city.

Passive immunization

In addition to active immunisation, in which the body itself has to form antibodies, passive immunisation is also available, which differs fundamentally from active immunisation. No healthy people are vaccinated, but those who are already ill are vaccinated. This makes sense because it can happen that the human organism needs help to defend itself against a pathogen. Then the appropriate antibodies (="defensive weapons") are injected. These then help him to fight the pathogen and defeat the disease. The big difference to active immunisation is that no pathogens are injected, but antibodies are injected into patients who are already ill and not healthy.

Interestingly, passive immunisation also takes place naturally in nature. Un- and newborn babies are usually unable to produce antibodies themselves or only very slowly. In order to protect the children, the mother passes antibodies on to the child via the umbilical cord (before birth) and via the mother's milk (after birth). Humans have thus also "copied" the principle of passive immunisation from nature.

Based on our example, imagine the scenario that the city is in danger of being overrun by the evildoers. In order to support the law enforcement officers, they will then give you the right tools to fight the attackers.


  1. Taylor LE, Swerdfeger AL, Eslick GD. Vaccines are not associated with autism: an evidence-based meta-analysis of case-control and cohort studies. Vaccine. June 17,2014;32 (29): 3623-9. https://www.ncbi.nlm.nih.gov/pubmed/24814559