Vaccines

• Vaccines are the preparation of killed or living microorganisms that produce immunity when administered into the body. Immunity is defined as the ability of the body to resist diseases.

Discovery of vaccination

• Smallpox was the first disease ever controlled by vaccination.

Immunity and its types

• Immunity is the ability of a person to fight against diseases causing pathogens. The study of immunity is called immunology. There are two types of immunity:
• Natural or in-born immunity: This type of immunity is present in the body since birth.
• Acquired immunity: The immunity acquired after birth or during the lifetime of an individual is known as acquired immunity. It may be active or passive.

i.Active immunity: This is produced by injecting a small quantity of antigen called the vaccine into the body.

ii.Passive immunity: In this immunity, the body does not produce antibodies, instead the readymade antibodies from some other animals are introduced for protection against a particular disease.

Types of vaccines

i.Killed vaccine: These vaccines are prepared by killing the pathogenic organisms by heat or UV- rays or alcohol or formalin or phenol, eg Typhoid vaccine and Cholera vaccine.

ii.Toxoid: These vaccines are prepared by destroying the toxic property of the toxins produced by organisms but retaining its antigenic property, eg. Tetanus toxoid and Amtidiphtheria toxoid

iii.Attenuated living vaccines: The pathogen is made weakened and non-virulent Examples- Oral Polio Vaccine (OPV), Bacille Calmette Guerin (BCG), Mumps, Measles, Rubella (MMR) vaccine, etc. provides active life long immunity.

iv. Antibodies as vaccines: A serum is used after a person or animal has been exposed to infection This serum contains antibodies against pathogens. It provides passive artificial immunity for some period only, eg. Anti-tetanus serum (ATS), Anti-rabies serum.

v. Antigen-like: polysaccharides of Pneumococcii and interferon (glycoproteins) are also used as vaccines.

Classification

1.  First generation vaccine

• Vaccine produced by conventional method using whale organism are called first generation vaccine.

2. Second generation vaccine

• Vaccine produced by genetic engineering or recombinant DNA technology are known as second generation vaccine. These vaccine are simpler, safer and more effective for eg: Hepatitis- B virus.

3.Third generation vaccine

• Vaccine which are produced artificially are called as third generation vaccine. These vaccine are more pure and highly effective at all. Eg.: vaccine for diphtheria.