What Is Immunization?

Immunization is an artificial method of making the body respond to an infectious agent such as a virus or a bacterium by giving it a vaccine. The vaccine is either the whole infectious agent, either dead or attenuated so it does not cause the actual infection, or is part of it. The body sees the vaccine as the real infection and responds by producing antibodies and a cell mediated immune response.

This sets up a memory of the infectious agent in the body and, if the person who has been vaccinated later comes into contact with the real infectious agent, they are able to mount a quick and effective immune response. They kill the viruses or bacteria before they can cause illness.

The first vaccination was developed against smallpox by Edward Jenner in 1796. He noticed that milk maids who often got cowpox – a similar but not very serious disease from cows – never got smallpox. He inoculated people with cowpox and showed they did not develop smallpox when they came into contact with it.

Vaccination has now completely eradicated smallpox from the world – the only virus stocks that remain are stored carefully in only a handful of laboratories for research.