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VVaccinationACCINATION
Vaccination refers to a procedure in which the presence of an
antigenstimulates the formation of antibodies. The antibodies
act to protect the host from future exposure to the antigen.
Vaccination is protective against infection without the need of
suffering through a bout of a disease. In this artificial process
an individual receives the antibody-stimulating compound
either by injection or orally.
The technique of vaccination has been practiced since at
least the early decades of the eighteenth century. Then, a com-
mon practice in Istanbul was to retrieve material from the sur-
face sores of a smallpoxsufferer and rub the material into a cut
on another person. In most cases, the recipient was spared the
ravages of smallpox. The technique was refined by Edward
Jennerinto a vaccinefor cowpoxin 1796.
Since Jenner’s time, vaccines for a variety of bacterial
and viral maladies have been developed. The material used for
vaccination is one of four types. Some vaccines consist of liv-
ing but weakened viruses. These are called attenuated vac-
cines. The weakened virus does not cause an infection but
does illicit an immune response. An example of a vaccination
with attenuated material is the measles, mumps, and rubella
(MMR) vaccine. Secondly, vaccination can involve killed
viruses or bacteria. The biological material must be killed
such that the surface is not altered, in order to preserve the true
antigenic nature of the immune response. Also, the vaccina-
tion utilizes agents, such as alum, that act to enhance the
immune response to the killed target. Current thought is that
such agents operate by “presenting” the antigen to the immune
systemin a more constant way. The immune system “sees”
the target longer, and so can mount a more concerted response
to it. A third type of vaccination involves an inactivated form
of a toxin produced by the target bacterium. Examples of such
so-called toxoid vaccines are the diphtheriaand tetanusvac-
cines. Lastly, vaccination can also utilize a synthetic conjugate
compound constructed from portions of two antigens. The Hib
vaccine is an example of such a biosynthetic vaccine.During an infant’s first two years of life, a series of vac-
cinations is recommended to develop protection against a
number of viral and bacterial diseases. These are hepatitisB,
polio, measles, mumps, rubella (also called German measles),
pertussis(also called whooping cough), diphtheriae, tetanus
(lockjaw), Haemophilus influenzaetype b, pneumococcal
infections, and chickenpox. Typically, vaccination against a
specific microorganism or groups of organisms is repeated
three or more times at regularly scheduled intervals. For
example, vaccination against diphtheria, tetanus, and pertussis
is typically administered at two months of age, four months,
six months, 15–18 months, and finally at four to six years of
age.
Often, a single vaccination will not suffice to develop
immunityto a given target antigen. For immunity to develop it
usually takes several doses over several months or years. A
series of vaccinations triggers a greater production of antibody
by the immune system, and primes the antibody producing cells
such that they retain the memory (a form of protein coding and
antibody formation) of the stimulating antigen for along time.
For some diseases, this memory can last for a lifetime follow-
ing the vaccination schedule. For other diseases, such as tetanus,
adults should be vaccinated every ten years in order to keep
their body primed to fight the tetanus microorganism. This peri-
odic vaccination is also referred to as a booster shot. The use of
booster vaccinations produces a long lasting immunity.
Vaccination acts on the lymphocyte component of the
immune system. Prior to vaccination there are a myriad of lym-
phocytes. Each one recognizes only a single protein or bit of the
protein. No other lymphocyte recognizes the same site. When
vaccination occurs, a lymphocyte will be presented with a rec-
ognizable protein target. The lymphocyte will be stimulated to
divide and some of the daughter cells will begin to produce anti-
body to the protein target. With time, there will be many daugh-
ter lymphocytes and much antibody circulating in the body.
With the passage of more time, the antibody production
ceases. But the lymphocytes that have been produced still
retain the memory of the target protein. When the target is pre-womi_V 5/7/03 10:59 AM Page 567