What is a Vaccine| 4 Types with Examples

After the birth of the baby, doctor advices to vaccinate him.

This vaccination schedule goes on for weeks to almost couple of years.

Many vaccines are administered as a means of resistance to various diseases.

Most common types of vaccines administered are polio, TB, diphtheria, typhoid, pertussis, measles etc.

Though it is an expensive procedure many governments across the world provide free vaccination.

This helps to counter infant death and also increase the life span of citizens.

What is a Vaccine?

Vaccines are humoral substances which are given to enhance the immunity of the body. The body is made ready to combat and prevent any disease causing microbe in future. It is a preventive health measure.What is a Vaccine

In simple sense, vaccine is a biological substance which is given to healthy living being. It helps the body to generate immunity to a specific infection. This technology was developed as a preventive measure against rampant infection in the world.

Without these vaccines it would be difficult to combat many deadly infections like polio, small pox, TB etc. Due to these vaccines, it was even possible to eradicate diseases like polio, small pox from many countries.

So what are vaccines made of: Vaccines are antigens which are extracted from specific disease causing microbes? These are administered to the healthy individual to prevent any further infection. So vaccines develop immunity for a said disease.

How do vaccines work

Human body or any animal has a immune system which protects from diseases causing microbes and infections. When a substance enters the blood stream from outside the body from other than digestive route, then the immune system gets alert to nullify and destroy the substance.

This foreign substance is identified by size and also nature of the chemical component of the foreign particle. Once the foreign substance is identified, the immune system develops anti-bodies and also triggers white blood cells especially macrophages to manage the foreign matter. The antibodies bind to the foreign body and nullify it such that it does not cause any harm or disturbance to the body’s physiology.

Similarly, the macrophages on the other hand, engulf (eat) the foreign particles like bacteria if identified.
In case of weakness or stress, the body’s immunity is not sufficiently alert to recognize the foreign particle or disease causing microbe. In such cases, the microbe might become virulent and take over the body physiology such that even immune system does not respond. This leads to disease in the individual.

To prevent this, the body’s immunity is prior trained to defend the infections. When vaccines (antigens or dead microbes) are administered to a healthy individual, the immune system produces suitable antibodies and macrophages to counter the antigens or microbes in the vaccine. In doing this it develops immunity to the disease causing microbe. So in future, if microbes for which vaccine were administered before infects the person. The immune system readily defends it and avoids diseases. This trained immunity lasts for few years to decades in most individuals. So administration of vaccines helps prevent infections in future.

Types of vaccines

There are 4 types of vaccines based on the type of antigen present in the vaccine. Sometimes the whole of microbe is given while only antigen from the microbe is given. types of vaccinesLive vaccine: As the name indicates, the vaccine is made of the real microbe which has been made weak and devoid of virulence. Here the microbe culture is treated such that it becomes weak and loses its ability to cause the disease. The weakened microbe is administered into the body. In the body, it does not produce the disease but instead the immune system gets activated. The antibodies and macrophages are produced so as to destroy the microbe. Thus after first exposure to the weak but live microbe, the body immune system is alert and can combat any future infections.
Ex: Polio vaccine

Dead Vaccine: Some of the microbes like bacteria are very virulent. Even if they are weakened, they can quickly recover their virulent nature and cause diseases. Hence to avoid this problem, the microbe is killed. The dead microbe is introduced as vaccine. The body develop immunity to this dead microbe based on the antigens present on the surface.
Ex: TB vaccine (BCG=bacillus colmett geurin): Dead mycobacterium tuberculous bacteria is used.

Sub-unit vaccine: As the name indicates, here instead of whole microbe, a part of it is taken. This part is sub-unit and it has potential to evoke immune response. This type of vaccine is avoids above problems of virulence and untoward infections. Further, the sub-unit vaccines can be less expensive as the whole microbe is avoided.

Genetically engineered vaccines: Most of the current vaccines fall into this category. These are produced by using the principle of genetic engineering. This types of vaccine not only avoid virulence but also can be produced in large scale. To cope up with vaccination demand of such large population, it would be difficult to produce the above type of vaccines. The vaccines of genetic engineering can be produced in large scale by rDNA technology. Also they are less expensive and more compatible than previous ones.
Ex: Hepatitis vaccines.


  1. sindhu

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