ImmunisationSpec 5.14
Immunisation gives protection from a disease without having to catch it. A person is given an inactive form of the pathogen, for example a dead or weakened one, usually by injection.
- The inactive pathogen is put into the body. It cannot cause the disease, but its antigens are still present.
- The antigens trigger an immune response and antibodies are made.
- Memory lymphocytes are produced.
- If the live pathogen enters later, the memory lymphocytes carry out a fast secondary response. Large numbers of antibodies are made quickly and the person does not become ill.
| Natural infection | After immunisation | |
|---|---|---|
| Pathogen present | Live pathogen | Inactive pathogen, which cannot cause the disease |
| Memory lymphocytes made? | Yes | Yes |
| Person becomes ill? | Yes, during the first (primary) response | No |
Doctors sometimes give a second injection, called a booster, to increase the number of memory lymphocytes made.