Definition – What is a vaccination side effect?
Side effects of vaccinations can be divided into vaccination reactions and vaccination complications. Vaccination reactions are relatively frequent. They occur in about two to 20% of the vaccinated persons.
The reactions to vaccination include harmless side effects such as redness or swelling at the injection site, but also a slight fever or a feeling of weakness and exhaustion. These symptoms are usually completely harmless and disappear again after a few days. The situation is different with vaccination complications.
These have become extremely rare today. Vaccination complications include severe and permanent side effects. For example, in the case of live vaccinations, it occasionally happened that the vaccinated persons developed the disease against which they had been vaccinated shortly before.
Causes of vaccination reactions
Vaccination reactions in the form of redness, swelling, pain at the injection site and mild general symptoms are harmless and indicate the normal reaction of the body to the vaccine. This reaction may vary in severity from person to person, so that some vaccinated persons may show symptoms but others may not. In both cases, however, the reaction is as follows: The vaccine contains antigens, for example, capsule or envelope components of bacteria or viruses.
The immune system recognizes the antigens as foreign to the body and the immune cells react with a slight inflammatory reaction. The area around the injection site is supplied with more blood. As a result, redness and swelling may appear.
Subsequently, the immune system starts to produce so-called antibodies. Some of these remain in the body for decades and can react directly and fight the antigens if they come into contact with the virus or bacterium against which the vaccination was administered. The vaccinated person does not become ill. Since every body reacts differently to the antigens in the vaccine, some people even experience a slight generalized inflammatory reaction, which manifests itself in fever or a feeling of weakness. Others do not experience any symptoms.
