Immunisation
The purpose of immunisation is to prevent
people from acquiring infections and to protect them
against short and
long term complications
of those infections . Vaccines work by stimulating bodies defence mechanism against infections . These defence mechanism are
collectively referred to as bodies immune system . The great
advantage of immunisation over natural infection is that immunisation
has a much lower risk of adverse
outcomes .
Immune system consists of
trillions of specialised blood cells known as WBCs and their products known as antibodies . These cells are located
throughout the body not only in
blood stream ,but also in lymph glands ,spleen ,skin ,lungs and intestine . The skin and lining of lungs are the first line
of defence against infections
.These tissues and WBCs located
at these sites
form innate immune system .WBCs
of innate immune system detect the presence of infection using sensors on their
surfaces that recognise
parts of pathogen or toxins released by them .These fragments from pathogen or toxins are collectively called antigens .
Lymphocytes are categorised into two types - B cells
and T cells . T cells respond to infections by releasing
chemicals called cytokine and B-
cells prepare complex
proteins called Antibodies which
attach in lock and
key fashion either to pathogen or
to toxin released by them .
Vaccine contain weakened
pathogens or antigens which generally do not have power to
cause disease .
Most
of cells involved
in immune responses live for
only a few days but small
number of lymphocytes survive for months or years after
infection has been cleared and retain a memory of invading pathogens .
Bodies immune system begins developing before
birth .Maternal antibodies cross the
placenta into babies circulation before
birth and are present in mother’s milk .Measles
containing vaccine (MMR) is not given until 12 months of age ,when maternal antibodies
against measles which can interfere with vaccine
responses have essentially disappeared .The following chart shows
the schedule of vaccination in
children –
Question 1 : Immunisation
Developing immunity against a disease through vaccine is comparatively safer than the immunity developed due to
natural infection . Give your arguments
in favour or against of the given statement .
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Question
2 : Immunisation Which
of the following vaccines
is given at the time of birth
to an infant -
i) BCG ,Hepatitis – B
ii) MMR
iiI) Hepatitis
– A
iv)
Rotavirus vaccine
Question
3 : Immunisation
Cells responsible
for immunity are short lived but
the immunity developed
after vaccination lasts for a
very long duration . How could it be
possible ?
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Question
4 :Immunisation
Why do
you think a particular vaccine should be
administered at a
specific age and not
randomly at any time ?
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Scoring key
Question 1 :
Immunisation
i)
Vaccine contains weakened pathogen or antigen which do
not have
power to cause disease but natural infection has active pathogens which
can cause disease -
Full Credit
ii) Any other answer - No credit
Question 2 :
Immunisation
Ans (i) BCG and Hepatitis B
Question
3: Immunisation
(i)
Small number of
lymphocytes survive for a
very long duration after
infection has been cleared
and keeps the memory
of invading pathogen . Full Credit
(ii)
Immune system works on memory
of infection - Partial Credit
(iii) Any other answer - No Credit
Question 4:
Immunisation
(i) Maternal
antibodies present in infants blood may interfere
with vaccine - Full
Credit
(ii)
Any other answer
- No Credit
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