a. Immunity. While most babies are born with a high level of immunity to many
disease organisms, this immunity is lost within a few months. The immunity possessed
by adults usually is acquired either naturally or artificially after birth and may be
temporary or permanent.
b. Antibodies. The basic component of immunity or specific resistance is the
antibody. Antibodies are proteins produced by the body system in response to
stimulation by a foreign substance (antigen) and having the capacity for combining
specifically with that substance. Immunization may be active or passive.
c. Active Immunization. In active immunization, antibodies are formed within
the body because of the presence of the natural infection (natural immunity) or because
of the inoculation into the body of infectious agents or antigenic substances derived
there from (artificial immunity).
In active immunity, a physical change is effected which is relatively slow
in developing (10 to 14 days), but whereby a permanent immune pattern is created.
While the level of active immunity may decline over a period of years, it is
susceptible to stimulation and elevation by a relatively small amount of immunizing
The immunizing material comprising the vaccine that is inoculated may
be either weakened (attenuated), killed (inactivated) disease organisms, or their
d. Passive immunization. In passive immunization, antibodies, which have
been preformed in humans, are injected into the body of a susceptible.
The duration of this type of immunity depends upon the persistence of the
injected antibodies and is usually not longer than a few weeks.
While immunity is immediate, no permanent immune pattern is set up.
Passive immunizations are used primarily in specific emergencies to
prevent hepatitis, rabies, measles in contacts, and tetanus in unimmunized wounded
7-16. TYPES OF VACCINES
a. Active Immunity. The Army uses three kinds of vaccines to induce active
immunity: attenuated live organisms, inactivated organisms, and products of organisms.
The type of vaccine must always be kept in mind when determining how a vaccine will
be used, since the responses differ.