WHAT IS VACCINATION?

INTRODUCTION

Vaccination is a preventive measure against infectious agents that may cause disease in an animal. In this process, we administer weakened antigens/products of an agent (virus or bacterium) or the whole agent either in the live, dead or attenuated form to the animal. The material administered is called a "vaccine". This ensures development of immunity to the concerned disease.

"LIKE PREVENTS LIKE"

The roots of vaccination ("vacca" means cow) lie in 1796 when a vaccine was first developed against the human disease "Smallpox" ("Chechak") by the British doctor Edward Jenner.

A patient infected with smallpox

In those times, another disease called "Cowpox" ("Gaay ka chechak") was prevalent in cows. Both smallpox and cowpox are caused by two related viruses i.e. these two viruses belong to the same family. Being from the same family, they share some common antigens/products on their surfaces.

Teat of a cow infected with Cowpox

Contact with cow udder

Cowpox infected individuals were relatively resistant to smallpox owing to the similar family of both viruses. Milking of cows infected with cowpox was the source of infection.

Milkmaid's hands infected with Cowpox

This "like prevents like" principle was used later for widespread vaccination of people against smallpox and we use the same principle in modern times to prevent diseases in animals.