Our body is constantly attacked by foreign elements such as bacteria, fungi or viruses that, upon entering our body, generate various diseases. These harmful elements are called noxas. Against this we have a defense system called the immune system, which works based on information. That is: the immune system, through its different elements, takes cognizance of the entry of one or more noxas and elaborates elements that are going to block them, these are called antibodies, and they are specific for each type of noxa. The system also has memory, in such a way that the structure of the noxas is recorded so that the next times they enter, the immune system already has knowledge of its structure and easily makes the necessary antibodies.
It happens that sometimes a noxa can enter that has the ability to quickly invade the body, and exceed the ability to analyze and produce antibodies, because the immune system has no knowledge of the structure of this foreign element and is overcome by the noxa, the consequences of which can be deadly.
The immune system can be informed about the structure of a noxa not yet known to it, making the “presentation” of the noxa so that it can learn and save this information in its memory. This presentation can be by entering the same artificially attenuated or dead noxa, since you only need to know what it is like. Or it can also be done through an intelligent system called a messenger, which contains only the information on the structure of the noxa.
This induced response system is called vaccination, and its origin dates back to 1798, the year in which Edward Jenner used the term "vaccine", derived from "cow", due to the studies he carried out on cowpox.
From that moment on, vaccines began to be prepared against a number of diseases and, thanks to this, thousands of lives have been saved.
With this foundation we can realize that the organism must prepare to have knowledge, file in its memory and be suitable (immunocompetent) for the entry of very harmful toxins. This is what vaccination is all about.
In summary, vaccines optimize the immune system, produce a positive reaction, achieve organisms prepared for the permanent attack of foreign elements that, due to their aggressiveness, can make our defense system give in.
It is necessary to mention that its role is to trigger a series of intelligent reactions on the part of the immune system and it is not possible that it can alter the genetic structure of our cells as many empiricists claim.