Immunity refers to the state of being immune to or protected from a disease, especially an
infectious disease. This state is invariably induced by having been exposed to the antigenic marker on
an organism that invades the body or by having been immunized with a vaccine capable of stimulating
production of specific antibodies.*
Interestingly, Pasteur’s practical aspects and Koch’s theoretical aspects jointly established the
fact that the attenuated microorganisms* retained their capacity and capability for stimulating the
respective host to produce certain highly specific substances i.e., antibodies** which critically protect
against subsequent exposure to the virulent organisms.***
Examples :
(a) Edward Jenner’s successful cowpox vaccine (in 1798) : Jenner’s epoch-making successful
attempts in vaccinating (innoculating) patients with cowpox vaccine, that ultimately resulted
in the development of resistance to the most dreadful smallpox infection.
(b) Pasteur’s successful rabies vaccine : Pasteur’s charismatic fame and reputation became
well known throughout France when he successfully prepared rabies vaccine by innoculating
a rabbit with the saliva from a rabid dog. The healthy rabbit contracted the rabies virus and
died later on. The extract of dead rabbit’s brain and spinal cord were duly attenuated and
injected into rabies patient who eventually survived later on. Thus, the vaccine for rabies or
hydrophobia — a disease transmitted to humans through bites of dogs, cats, monkeys, and
other animals.
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