Vaccines - A Primer
Part Two -- Design Issues --
Clinical Trials
Vaccines are a class
of treatment designed to treat a condition by activating a patient's immune system.
There are two basic classes of vaccines (based on purpose):
Therapeutic
Vaccines: The intended effect of
these vaccines is to treat or eliminate a condition by employing the immune
system, or by otherwise interfering with the pathogenic organism.
Prophylactic
Vaccines: The intended effect of
these vaccines is to prevent a condition by employing the immune system.
There are several classes of vaccine (based
on content):
Acellular: The
pathogenic (disease-causing) organism is not present in the vaccine.
Inactivated/Killed: The pathogenic organism is present (but
destroyed/dead/inactivated) in the vaccine.
Attenuated/Live: The pathogenic organism is present (but damaged) in
the vaccine.
Synthetic:
The active material in the vaccine is not directly derived from the pathogenic
organism.
A Short and Crude History of Vaccination
Small-Pox and Variolation
The Chinese
employed variolation in the prevention of small-pox.
This process involved the transfer of small-pox lesion
fluids (pus) into the skin of uninfected persons.
Horses and Cows
and Milkmaids
Circa 1700's, E
Jenner noted the connection between Smallpox and Cowpox. Jenner infected
various human subjects with cowpox, and after their recovery exposed them to
smallpox. The prior exposure to cowpox effectively protected the people from
smallpox.
This experience is
the reason that this basic process is called vaccination - vaccas
is latin for cow.
Salk and Sabin and Poliovirus Vaccine
As a class of treatment, vaccines of one form
or another have been employed since antiquity. The earliest forms of vaccine
were based on material derived directly from infected persons. The material was
then directly introduced to uninfected people.