It is helpful to discuss some vaccine terminology in order to understand how vaccines work.
A vaccine is a biological preparation that induces an immune response to a certain pathogen without causing the disease itself and also creates immune memory so that a person can respond to that pathogen upon subsequent exposure, hopefully preventing the disease. Examples of vaccines that are routinely used in the U.S. are measles, diphtheria, tetanus, pertussis, and many others.
In passive immunization, the person acquires immunity by receiving antibody-containing products to help fight the disease immediately. However, with passive immunization, a memory response does not develop so an individual has no protection to subsequent exposures. An example is a preparation of antibodies to the rabies virus that can be given if a person is exposed to rabies. The immunity that an infant acquired in utero from its mother could also be considered a passive form of immunization.
Immunization refers to the process by which a person acquires resistance to a disease (i.e., immunity), from a vaccine. The words vaccine and immunization are often used interchangeably. However, immunization can also occur naturally, that is from contracting the disease.
Vaccinology is the science of vaccines which includes a diverse group of topics:
- nature of immunogens—the part of the microbe that triggers an immune response
- host immune response itself
- actual engineering and development of the vaccine
- vaccine delivery strategies
- manufacturing
- clinical evaluation
