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Vaccinations. The immune system shield

13/01/2021 Epidemiology

We live with harmful agents daily, naturally present in our environment. The body has defenses to prevent the entry of these pathogens, such as mucus, that act as a physical barrier to prevent the passage of microorganisms into our system.

However, if a pathogen manages to find its way and infect the body, one of the most robust and wonderful systems is activated, i.e. the immune system, the most powerful defense machine whose goal is unique and simple: identify, attack and destroy the harmful agents present in the body.


Generally speaking, pathogens are referred to as harmful agents that infect the body, which can be bacteria, viruses, parasites, or fungi, responsible for triggering diseases. Each of these agents is composed of different parts, making it unique, differentiating it from the others. Only one of these parts is the one that initiates the disease and is known as antigen.


The response of our immune system occurs when it recognizes the antigen, generating antibodies to combat it. To understand it simply, the antigen is the enemy's soldier and the antibody is the defense soldier.



Part of the magic of our immune system is the variety of antibodies it develops, just as the flu does not feel the same as diarrhea, the antibodies generated to fight are developed specifically to attack one disease or another, as if we had battalions of soldiers trained strategically to attack the weak points of every enemy it faces, and our body is capable of learning and developing thousands of different battalions.


Much of our survival on this planet is due to the responsiveness of our body to successfully cope with disease, yet our immune system has had to learn how to fight first. When faced with a disease for the first time, the organism takes time to respond and produce the specific antibody against the antigen and thus reject it.


But it doesn't end there, not only does the body respond by developing antibodies specific to each disease, but also generates a memory bank so that, in case of a new attack of the same disease, it knows how to react and eliminate it, by perfecting the technique.



If our immune system is so powerful, what's the problem then? It can have several variables, to name some:

  • Time to respond. When the pathogen is new, it takes time for the organism to generate the antibody and depending on the degree of virulence (toxicity) of the disease, it can cause serious problems in the system before it can be combated.
  • Immunosuppressed people. Not all people have a strong immune system, there are certain conditions (developed or born with) that compromise it and do not allow them to function as such.



Fortunately, science has evolved greatly and has developed defence mechanisms that support the work of the human body, and one of the great medical advances of all time has been the development of vaccines that have effectively combated potentially lethal diseases such as meningitis, tetanus, measles, and polio.


Vaccines function as a “domesticated enemy”, that is, the weakened or inactive antigen of a given disease is created in a laboratory, so that, when entering the body, our immune system has time to learn how to fight it without the danger of a real and functional antigen: it is active enough that the specific battalion against the disease is generated, but not so strong to develop the disease.


In this way, if in the future the body is exposed to the real disease, it activates the defence memory that his learning with the vaccine left him to fight it.


Some vaccines are single doses and others are multiple doses with waiting times, which depends on how the vaccine is designed and the need for reinforce it that must have the body.



So far, we have talked about vaccines and their effect on the body in a unique way, that is, how it develops and acts in a person, but there is a very positive side effect called “Collective Immunity”.


The lines above speak of people whose immune system does not work properly, either because of pre-existing or developed diseases. For example, a person with cancer has a weakened system from fighting this disease, so if suddenly another pathogen enters the same body, the immune system may not be able to respond.


There are also people who are allergic to certain components of developed vaccines, people who, due to the excessive reaction of their bodies to certain agents, cannot be vaccinated, leaving them unprotected from certain diseases.


For these people their best support is their community. When many people in a community have defenses against a disease, the pathogen cannot circulate because it is rejected, which closes ranks in favor of those who cannot be vaccinated and are therefore protected.


It is important to comment that collective immunity is not something that happens immediately, like everything else, it takes management time, so it is advised even after receiving the vaccine to keep the corresponding precautions to avoid contagion.


Finally, it must be remembered that no vaccine alone provides 100% protection, however, it has been widely proven how much they help to eradicate diseases in the world.






"How Do Vaccines Work?", World Health Organization,


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