Immunisation is an example of primary prevention and is one of the most effective public health interventions. Immunisation refers to the process of developing immunity to certain diseases by injecting antigens or serum containing specific antibodies. Although the terms vaccination and immunisation are used interchangeably, vaccination in the strict sense of the term refers to the process of inoculation to provide immunity using cow pox (vaccinia) to prevent smallpox (Box 31.1).
Although the mechanisms are complex, there are essentially two broad categories of immunity:
- innate or non-specific