What is Vaccination? Mention the four ways in which vaccines are prepared, giving the name of one disease for which each type of vaccine is used.

Vaccination is the practice of artificially introducing germs or germ substances into the body for developing resistance to particular diseases. The material introduced into the body is called the vaccine. Usually, the vaccine is introduced into the body by injection and sometimes orally.
A vaccine can be prepared by any one of the following four methods —

1. Using killed germs — e.g. TAB vaccine for typhoid.
2. Using living weakened germs — e.g. the vaccine for measles.
3. Using fully virulent living germs — e.g. the vaccine for smallpox.
4. Using Toxoids — e.g. the vaccines used for diphtheria and tetanus.