Active immunization:-
It is the administration of antigen to the host in order to
induce antibody production.
Vaccines are used for active immunization.
Vaccines are suspensions of micro-organisms (dead or
live attenuated) which stimulate the immunological
defence of the host by developing antibodies.
They impart active immunity, which takes sometime to
develop & thus used prophylactically – the antibodies
so developed destroy the specific micro-organism when
it enters the body.
LIVE ATTENUATED – BCG, Typhoid, Polio, MMR
KILLED
(INACTIVATED) – Rabies, Cholera,
Hepatitis A,B. Pertussis.
Toxoids:-
Bacterial exo-toxins modified to remove toxicity but
retain antigenicity are toxoids.
E.g. – Tetanus & Diphtheria.
Passive immunization:-
It is imparting immunity to a host passively by the transfer
of antibodies. E.g. – Antisera & immunoglobulins (Ig)
This affords immediate protection as readymade antibodies
are available.
Antisera like tetanus antitoxin, gas gangrene antitoxin,
diphtheria & antirabies serum are obtained from serum of
horses which are actively immunized against the specific
organism.
Sensitivity testsshould be done before giving antisera.
Immunoglobulins:-
They are human gamma-globulins that carry the
antibodies – like normal human gammaglobulin,
tetanus
Ig,
rabies
Ig,
anti-diphtheria
Ig
&
Hepatitis – B Ig
Allergic reactions including serum sickness &
anaphylaxis can occur with antiserum, while it is
uncommon with Igs.
Primary immunization:-
It provides primary immunity & is usually given in
children E.g. – DPT.
Secondary immunization:-
It is done to reinforce the primary immunity by giving
booster doses.
