1-11. ACTIVE IMMUNITY
a. Immunity acquired naturally is called active immunity. An individual can have
the disease, recover, and become permanently immune. Measles, chickenpox,
whooping cough, scarlet fever, typhoid fever, Rocky Mountain spotted fever, and
diphtheria are examples of such diseases. The person has chickenpox, recovers, and
has a permanent immunity to chickenpox. There are other diseases which an individual
can have and recover from but not develop a lasting immunity. The group of infections
called "the common cold," influenza, gonorrhea, septic sore throat, and some types of
pneumonia are examples. A person can have a cold, recover, and get another cold.
b. When an individual has a disease, antibodies form within the body in
response to the stimulation of natural infection or of infectious agents. The antibodies
develop slowly, usually after about 10 to 14 days. The length of time the immunity lasts
varies depending on the disease.
1-12. ARTIFICIAL IMMUNITY
It is not always convenient or desirable for an individual to have a disease in
order to become immune to that disease. Scientists, therefore, have developed artificial
processes, such as vaccination, which simulate nature but which are adapted to meet
practical requirements and which are under human control. Two major types of these
processes are active artificial immunity and passive artificial immunity.
a. Active Artificial Immunity. There are several ways of achieving this
immunity: injection of living, attenuated, or harmless organisms; injection of dead
organisms; and injection of bacterial exotoxins.
(1) Injection of living attenuated (weakened) or harmless organisms. This
type of immunity can be acquired by artificially imitating nature's method of mild
infection thus producing immunity. Smallpox, polio, rubella, measles, mumps,
adenovirus, and yellow fever are examples of diseases in which an active artificial
immunizing agent is used.
(a) Smallpox. The virus vaccinia, which causes cowpox in cows, when
transmitted to humans in a vaccination causes a mild condition at the site of the
vaccination. This is sufficient to give an individual protection from smallpox for a period
of from one to ten years, depending on the person and the environmental conditions.
1 The vaccination is performed on the arm over the deltoid
muscle. Clean the site gently. Energetic cleansing may create abrasions which may
become infected forming "satellite lesions." Apply antiseptics such as ether or acetone
(not alcohol) and allow the site to dry thoroughly. Failure to allow the antiseptic to dry
may cause the vaccine to be inactivated.