Vaccine and it’s role in inducing immunity

To fight against a disease, it is very important for us to build a specific immunity (active immunity) against the pathogen or pathogenic substance, causing the disease. The process through which immunity is produced in an organism is called immunization. It is mainly two types-Passive immunization and Active immunization. The active immunization is mainly done by injecting vaccine and it has an important role in inducing our immunity. And the injection of a vaccine in an organism is known as vaccination.

DEFINITION OF VACCINE: Vaccine is a non-pathogenic antigenic substance (may be killed or inactivated pathogen or some parts of the pathogenic organism), which produce acquired immunity to a particular disease. When it is injected in the body it starts to mimic the pathogen and induce our immune response (both humoral and cell mediated) to provide protection against that specific pathogenic material.

Vaccine of Influenza

Vaccines are mainly classified into two type: 1. Whole organism vaccines, 2. Purified antigen vaccines.

WHOLE ORGANISM VACCINES: When the whole-body part of a pathogenic organism (may be killed or attenuated) is used in the preparation of vaccine. This is further classified into: a. Live but attenuated vaccines and b. Inactivated or killed vaccine.

  1. Live but attenuated vaccines: In this type the pathogenic organism loose it’s pathogenicity but retain immunogenicity which is done by attenuating the pathogen growing it in unfavourable condition which results gene mutation. Example: Vaccine of tuberculosis- Bacillus Calmette Guerin (BCG).
  2. Inactivated or killed vaccines: In this type the pathogenic organism is inactivated or killed by heat or chemical treatment. Example: Salk Polio Vaccine.

PURIFIED ANTIGEN VACCINE: It is prepared by purifying the pathogenic toxoid material and it retain antigenicity. These are two types- a. Toxoid vaccine, b. Capsular polysaccharide vaccine, c. Recombinant antigen vaccine.

  1. Toxoid vaccine: They retain antigenicity but loose toxicity. It enhances T-cell response. Example: Diphtheria vaccine and Tetanus vaccine.
  2. Capsular polysaccharide vaccine: It is poorly immunogenic and dose not stimulate T-cell. Example: Hib vaccine for H. influenza type-b.
  3. Recombinant antigen vaccine: It induces humoral and cell mediated immunity. Example: Hepatitis -B vaccine.

Vaccine and vaccination are very important for us to fight against a disease. 

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