Annual Report 2003 Aventis - Sanofi

Medical Background
Immunization primes the body’s own immune
system to prevent diseases caused by specifi c
viruses and bacteria. It helps the immune system
to build its defenses against these organisms so
that when an immunized person is exposed to the
disease, the immune system can mobilize quickly
and effectively to prevent infection.
Immunization works by exposing the body to
vaccines, usually by injection. Vaccines contain tiny
amounts of material that stimulate the immune
system to produce antibodies and special cells
aimed at a specifi c virus or bacteria. The immune
system stores this information. Later, even many
years later, when the immunized person is exposed
to that virus or bacteria, the immune system
remembers how to respond. It can then produce
the appropriate antibodies and cells quickly and in
large amounts. This prevents the virus or bacteria
from becoming established in the body and causing
infection.
The microcosmos of the immune system
Macrophage
Granulocyte
Messengers
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