Immunization is the artificial confirmatory
resistance to infectious diseases. It is the acquisition of specific immunity
to particular disease by injecting antigen or antibodies. Immunization induces
a “primed state” in the patient such that on first contact with the relevant
infection, a more rapid effective secondary immune response will be mounted
leading to prevention of disease.
Vaccination is like a “cram” course i.e forced study
by memorization for the immune system making it to recognise and fight off
potential invasion by hostile microbes. Vaccination depend on the ability of
the B and T- lymphocytes to respond to specific antigen and develop into memory
cells, thereby representing a form of actively enhanced adaptive immunity.
The aims of immunuzation
most important is the eradication of disease.
protection of individuals against the infection
protection of the individual against the symptom or pathology where the
presence of the microbe is not itself harmful.
block transmission as in the case of a vector-borne disease with a well defined
effective stage without benefiting the vaccinated individual at all.
The properties of a good vaccine
To create effective vaccines, scientists must
understand the immune system’s complete network of cellular “sentries”. These
are the cells that detect pathogens and the soldiers which attack and destroy
them. A good vaccine should be effective, safe, stable and cheap as far as
Effectiveness: A good vaccine must be able to induce
an adequate response of the right type. For instance, a pure antibody response
will be useless against T.B while a pure cell mediated response will be useless
against Streptococci pneumonia, in
another instance, high level of serum antibody may be irrelevant to mucosal
protection against polio while the activation of cytotoxic T-cells may be
positively harmful in Hepatitis.
Duration of response: This is very important in
specific cases for example, short term protection will be achieved where the
vaccine merely induces the presence of antibody. On the other hand, for the
long term protection memory cells will be required and they will be needed for
protection at some time in the future. Living vaccines induce storage and more
lasting immunity than non-living vaccine.
Safety: A good vaccine must not induce damage in the
people vaccinated considering that vaccine are the only compounds routinely
administered to perfectly healthy people. There should be rigorous safety
testing requiring extensive quality control and animal testing.