What are the different types of vaccine?Explain how vaccine work
against infectious disease?
Vaccine is a biologicaly synthesized substance that
provide long lasting immunity against infectious disease by giving an antigenic
These vaccine are prepared from dilute substance
that is partially or completely deprived
of pathogenicity and provide immunity by activating immune system .They replicate in the host cell and
give antigenic stimulus .Inadequate administration or storage is the cause of
primary vaccine failure ,however it is
very rare.Live vaccine is unstable
against heat .It can not be given to pregnant women or immunologically weak
persons as it can cause disease in them.It provides systematic and local
Early examples of the use of this type of vaccine is
cowpox used to control the smallpox.
Other examples of live vaccine are polio vaccine ,anthrax vaccine etc.
Heat killed vaccine:
Heat killed or
chemically treated disease causing viruses or bacteria are used to form these vaccine .Formaline
,merthiolate and phenol are the chemicals that are used for this purpose .For
activation this must have more antigen as compare to live vaccine which are
capable of replication in the host cell.It can not induce local immunity .It is
safe and stable ,so can be given to pregnant women.
Examples includes pertussis,
TAB,Salk and semples vaccine that are used to cure whooping cough,entric
fever,poliomylits and rabies.
3. Subunit vaccine:
To prepare this type of
vaccine we use those specific fragments of viruses and bacteria that are best
to stimulate the immune response .These
are nonreplicating vaccine that are produced by the natural preparation of virus from the animal tissue. Examples
includes HA vaccine used against
influenza A and B.
Toxin of bacteria are
treated by the formalin to destroy its
toxic nature but its antigenic ability retain.Examples includes tetnus and
In this vaccine DNA
coding for foreign antigen entered directly into host so it producec directly
by it.This vaccine would be highly safe and have no side effects.Moreover it
needs less time to prepare and provide long term immunity when inserted into a
non-dividing tissue such as muscle.
MECHANISM OF VACCINE
WORK AGAINST DISEASE:
When a vaccine is
introduced in bloodstream,it is trapped by the APC cells which are finding the
invaders around.They detects them ,ingest it ,break it ,and show a part of
antigen on its surface.Then it move towards the lymph nodes where naïve T cells
are activated as when they recognize the
antigen as foreign.T helper cells then activates the surrounding cells.
Some of the naïve B
cells gets mature into B plasma cell and produced Y shaped antibodies against
foreign antigen.Every antibody attach tightly with specific target antigen making lock and key model
which prevents the antigen from entering the cell or destroy it.If vaccine
viruses are weak ,they entered into the cells where they are killed by killer T
cells.Killer T cells,B cells and T helper cells memorize the Pthogen for future
.As the result of this memorization ,the body response to specific pathogen
will be faster and stronger than before.This is known as secondary response to
So ,the vaccination
program help the immune system to memorize
the specific disease causing bacteria or viruses by practicing with
inactivated,weakend or killed version ..