Throughout history, mankind has fought for the right to live happily ever after on this planet. People had to deal with all sorts of challenges such as natural disasters, threats of predators and insects, famine, war, etc.

But the harshest ordeal is an epidemic that has always been at the top of the list. In the Chronicles of control of epidemics and pandemics, there are pages describing infections that destroyed cities, entire regions, and even civilizations. Outbreaks of infectious diseases caused the most awful horror; people dedicated all their resources to fight them.

In the beginning, we were completely helpless and one of the main reasons was a lack of knowledge. Over time, different abatement techniques have come along. We have progressed from chasing evil spirits away to the development of recombinant vaccines, antibiotics, and antivirals.

Why can’t an individual cope with the infection himself? Let us work this out.
Any microorganism consists of various proteins which our immune system tries to recognize and destroy. Phagocytosis is the first and evolutionary oldest defense mechanism. Phagocytes, border dendritic cells form a widely distributed cellular system throughout the body: skin, intestinal track, mucous secretions in the respiratory tract. When anything appears, which is not marked as «friendly», these cells capture and cleave the object. However, this is not enough to ensure effective fighting.

One of the drawbacks is that trespasses being found are not memorized, so each time you have to make a fresh start. There is a huge variety of microbial heterologous proteins. In some cases, it is a matter of life and death to make a quick assessment and respond promptly to a threat.

Therefore, we have lymphocytes, the elite troops, which have special receptors on their surface that identify a particular heterologous protein in a personalized manner. After contacting this protein, some of the lymphocytes transformed into a plant for producing antibodies that destroy the intruder or evolves killer cells; the other part becomes memory immune cells so that the next penetration of the same antigen will be instantly detected and eliminated.

This scenario does not describe all the victories of our body. Why? If we don’t discuss disease states that lead to reduced immunity, the answer to this question can be found in the desire of microorganisms to live. To overcome our body’s defense mechanism, these foreign invaders have also learned to adapt and fight. Some examples of creating such protection are quite admirable. In these cases, an individual cannot cope without external assistance.

Currently, vaccines are one of the most powerful weapons in the arsenal of homo sapiens. It is precisely through them that we defeated such terrible diseases as smallpox, poliomyelitis, rabies, measles, etc.

Principle of vaccine is quite simple. Such medication contains a weakened or killed pathogenic microorganism and its proteins in some cases, which can cause an immune response. After the introduction of the vaccine to the body, the same process described above takes place and immunity is well suited to respond from this point.