b. Passive. In passive immunization, antibodies that have been preformed in
humans or animals 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. Therefore, passive immunizations are used primarily in specific emergencies
to prevent hepatitis, rabies, pertussis in babies, measles in contacts, and tetanus in
unimmunized wounded individuals.
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.
(1) Live organisms. Vaccines that consist of suspensions of attenuated
(weakened) live organisms--bacteria or viruses--include smallpox, poliomyelitis, yellow
fever, measles, mumps, rubella, and adenovirus. A single injection of such a vaccine,
properly prepared, stored, and used so that it retains required viability (potency), usually
provides a fairly rapid, ample, and lasting immune response.
(2) Inactivated (killed) organisms. Vaccines made from inactivated
organisms include influenza, typhoid fever, cholera, plague, and rabies. A single
injection of most inactivated vaccines may produce only a scarcely detectable response.
The first injection, however, orients the body so that subsequent injections produce
successively larger responses. It is for these reasons that immunization against typhoid
fever, cholera, typhus, tetanus, and other diseases for which nonliving vaccines are
utilized is carried out by a series of injections.
(3) Products of organisms. Toxoids consist of chemically inactivated
bacterial poisons injected into individuals to induce the formation of antibodies against
the original bacterial toxin. The two commonly used toxoids are tetanus and diphtheria
b. Passive Immunity. Passive immunity depends upon the presence of
injected, preformed antibodies. The source of such antibodies is serum globulin, a
concentrated fraction of blood plasma from human beings or animals. Immune serum
globulin (gamma globulin) contains the dominant form of antibodies found in the blood
of normal adult human beings. In practice, it has been found to be of value as a
prophylaxis against type A hepatitis, measles, and, in a marginal sense, of poliomyelitis
and rubella. Immune globulin preparations for measles, vaccinia, pertussis, mumps,
rabies, and tetanus are obtained by hyper-immunization of human beings or from
persons with high antibody titers.