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Vaccines:
What are they and how do they work?
A vaccine is any preparation of medicinal substances which stimulate immunity
against a specific pathogen, such as a virus or bacterium,
in the body to which it is administered. Once people are immune to a pathogen,
they cannot become infected by it.
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Vaccines
induce immunity by stimulating production of pathogen-specific antibodies.
Vaccines do not cause disease.
When a vaccinated person becomes exposed to the pathogen, the antibodies
recognize the invaders and destroy them.
Vaccine-induced antibodies remain in vaccinated people for an extended
period of time, warding off infection when they are exposed to pathogens.
The length of time over which vaccines are effective varies. Some
last a lifetime, while others only work for a few months. |
There are four main classifications of vaccines, each corresponding to the
method by which it is made. Each
type of vaccine functions in a slightly different manner. Specific
diseases require certain kinds of vaccines. The four types are live-attenuated,
killed viruses, components of viruses, and toxoids of pathogenic bacteria
(Okonek).
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