Immunisation

Immunisation is the process of introducing harmless preparation of the antigens from an infectious agent into the body of a person, who becomes immune to the infectious agent as a result. The harmless preparation of antigens is called a vaccine (pronounced "vax-een"). It is made from killed or weakened viruses or bacteria, or antigens extracted from the infectious agents. Immunisation should happen before the person develops a vaccine-preventable infection, so vaccines are usually given to babies and young children, either by injection or swallowing liquid drops. However, you should note that there are many communicable diseases that cannot be immunised against at the present time, because a suitable vaccine does not yet exist.