Vaccination is the process of protecting against
disease by introducing dead or otherwise
weakened infectious organisms (known as
antigens) into the body. The weakened infectious
organisms causes the body’s immune (defense)
system to produce antibodies and memory cells.
Antibodies are types of proteins that help stop
future infections by the same antigen. Memory
cells are types of white blood cells that remain in
the body in a resting state after many of the other
Above: The MMR (Measles, Mumps,
Rubella) vaccine used for children.
infectious organisms. Memory cells “remember" antigens they were exposed to in the
past so they can deal with them in a quicker and stronger way when exposed to them in
Since the infectious organisms introduced to the body through vaccination are
weakened, and thus presented to the body in an altered state, they will not actually
cause disease. By preparing the body with a stock of antibodies and memory cells
against a specific disease, vaccination helps defeat the illness and prevent infection if
one if exposed to the actual bacteria or virus in the future. When this process is
successful for a specific disease, the person is said to be immune to that disease.
The process of achieving immunity is referred
to as immunization. The preparation of
antigens injected into the body is known as a
vaccine. Vaccination comes from the Latin
word "vaccinus" meaning "relating to a cow."
The reason for this word origin is that the first
vaccine (the cowpox virus) was obtained from
cows. The cowpox virus was a relatively
benign (mild) virus that was discovered to lead
to immunity to smallpox, a type of deadly and
highly contagious disease.