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1. IMMUNIZATION IN PEDIATRIC PATIENTS
IMMUNITY
The term immunity refers to resistance exhibited by the
host towards injury caused by microorganisms and their
products.
Protection against infectious or pathogenetic agents is
only one consequences of immune response, which in
entirely is concerned with reactions of body against any
foreign antibody. Immunity hence by different mates plays a
significant role in normal life of an individual without which
survival is almost compromised.
Study of immunity has a long history where in 1718
(18th
century) people used small pox infectious sites for
inoculation in their children at an early age. This proved
very much successful by preventing further attack of small
pox in children at on older age. This began the process or
method of immunization of children so as to prevent further
attacks from a similar organism.
1

2. Types of immunity:
Immunity against infectious agents is of different types
namely:
1. Innate immunity:
a) Specific Species
Racial
b) Non specific Individual
2. Acquired immunity:
Acute Natural
Artificial
Passive Natural
Artificial
Innate immunity:
Innate immunity or native immunity of an individual is
the immunity, which an individual possesses by virtue of his
genetic and constitutional make up.
It does not depend upon the caries contact of an
individuals with infectious agents or immunization.
2

3. It may be non-specific when the degree of resistance to
an infection is considered in general or specific when
resistance to a particular pathogen is concerned.
Innate immunity is considered at the level of species,
race and individual.
Immunity at the level of species is shown by total or
relative refractoriness to a pathogen shown by all individuals
of a species. For example, human beings are resistant to
infections from plant pathogens and to pathogens of animals.
The mechanism of this immunity is not understood
fully but may be due to changes in physiological and
biochemical properties between tissues of different host
species which determines whether or not the pathogen can
grown in them.
Racial immunity is evidenced by differences in total
resistance capacities of individuals of different races. It can
be seen mainly in animals. In human beings it is seen that
the overall resistance of negroes is more when compared to
whites. Infections like malaria are more frequently in whites
when compared to negroes possibly because, the high
incidence of sickling (sickle cell carcinoma) provides
3

4. resistance against malaria organisms. Each racial differences
are known to be genetic in origin and by selection and in
breeding possible to develop at will races that have higher
degree of resistance or susceptibility to various disease
pathogens.
Immunity (innate) at individual level can be considered
under various aspects as follows:
1. Age: Two extremes of life present with increased
susceptibility to infections. The immune system
in children is weak as it is still in a developing
stage. In fatal life infections are reduced by
immune system of mother. In younger age
increased susceptibility may be due to hormonal
alterations. As the age is progressed towards old
age the immune system gets waned and again
susceptibility to infections is increased.
Hormonal Influences:
Endocrine disturbances like diabetes, adrenal
dysfunction, hypothyroidism etc are activated with enhanced
susceptibility to infections. In all these cases immune
mechanisms are compromised. The corticosteroids suppress
4

5. immune system by their action as anti-inflammatory and
antiphagocytic. At the same time steroids also exhibit
properties like neutralization of bacterial endotoxins.
Nutrition:
The relation between nutrition and immunity very
complex. In general both cell mediated and humoral
immunity are reduced in malnutrition.
It is also seen that certain conditions may not be seen
in severely ill patients. The malarial infection in very severe
illness may not induce fever but when diet (nutrition) is
improved it may produce fever. It is found hence that certain
viruses and bacterias can not grow in cases of severe illness.
Mechanism of Innate Immunity:
Skin and mucous membrane:
An intact skin and mucous membrane provide
considerable protection against invasion by microorganisms.
Healthy skin possesses bactericidal property by means
of high concentration of salt in drying, sweat. The sabecious
glands and long chained free fatty acidic also impart a
protective action against microorganisms.
5

6. Mucosa of respiratory tract has several innate
mechanisms to provide immunity. Before the air could enter
the lungs starting from the point of entry of air into nasal
orifices the air is filtered to remove all impurities, the larger
particles are removed in nasal cavity by ciliac and mucous
secretions. The smaller particles which escape from nasal
cavity are removed by mucous secreted along the bronchus.
Once the particles are caught they are ultimately coughed
out. Any other small particles escaped through these ways
are removed by phagocytes in respiratory alveoli.
Mouth is constantly bathed by saliva which has several
antibacterial properties. The particles in mouth are subjected
to various digestive juices and ultimately digested. Strong
acidic pH in stomach helps in fighting against many
organisms. If organisms can survive in acidic environment
these are ultimately killed in intestine when the pH of
secretions increases gradually and becomes alkaline.
Intestinal mucosa consists of normal microbial flora
which prevents further colonization by other organisms.
Conjunctiva is freed from foreign particles by the
flushing action of lacrimal secretions. Tears contain
6

7. lysozymes, an antibacterial substance in them. This lysozyme
is in an amount present in lacrimal fluid mainly active
against gm positive non pathologic cocci, lysozymes are
present in all of the tissue fluids and secretions except in
C.S.F. sweat and urine. It has been found that phagocytic
cells contain significant amounts of lysozyme in them to be
active against majority of athogenic organisms.
Flushing action of urine frees the bacteria from
urethra.
Antibacterial substances in blood and tissues:
Complement system possesses bactericidal properties
and plays an important role in destruction of pathogenic
organisms that invade blood and tissues. Propordin a
substance present in normal serum combines with
complement an mg++ ions lysis of gm negative bacteria and
also some viruses.
Several other factors having antibacterial property in
blood are:
1. Beta lysine – A relatively hemostable substancec active
against anthrax and related bacilli.
7

8. 2. Basic polypeptides like lukins secreted from
leukocytes and plakin secreted by platelets.
3. Lactic acid in muscles and in inflammatory zones.
All these substances exhibit antibacterial properties.
Cellular factors in Innate Immunity:
Natural defence against invasion of blood and tissues
by microorganisms and other foreign particles is mediated to
a larger extent by phagocytic cells, which ingest and destroy
them.
Phagocytic cells are classified as microphages and
macrophages. The microphages consist of
polymorphonuclear leukocytes. Macrophages consist of
wandering ameboid cells. Cells of reticuloendothelial system
and monocytes.
A major function of RE system is removal of foreign
particles that enter the body. The phagocytes reach the site
of inflammation by different chemotactic substances and
ingest the foreign bodies. The bacterias are phagocytosed
into a vacuole which combines with lysosyme to form
phagolysosome. The phagolysosome is subjected to various
lytic enzymes to destroy the organism.
8

9. Inflammation:
Tissues injury or irritation initiated by the entry of
microorganisms leads to inflammation which is an important
nonspecific defense mechanism. The blood vessels constrict
initially followed by dilatation. The processes like
margination ad diapedesis and emigration of leukocytes from
blood vessels to inflammatory site takes place which leads to
phagocytosis.
Fever an increase in overall body temperature is also a
defense mechanism mainly by inhibiting in growth or
destroying pathogenic organisms.
Acquired Immunity:
The resistance that is acquired during life of an
individual is known as acquired immunity. It is different
from innate immunity which is inborn.
Acquired immunity is of two types namely:
1. Active immunity.
2. Passive immunity.
9

10. Active immunity:
Active immunity is the resistance developed by an
individual as a result of an antigenic stimulus. This involves
active functioning of persons immune system leading to
synthesis of antibodies and / or immunologically active cells.
Active immunity sets in only after a latent period
which is required for the immunologic machinery to set in
motion. During the development of active immunity there is
often a negative phase during which, the measurable
immunity is lower than the immunity present prior to
exposure to an antigen.
This is seen because, during the process or period of
initial exposure, the antibodies normally present are utilized
for phagocytosis and therefore there is a net reduction in
total immunity. Once the immunity sets in it increases
rapidly and remains for a longer period of time. A second
similar exposure leads to setting of immunologic response at
a very faster rate and more efficiently.
Active immunity is characterized by immunologic
memory. This means memory of prior antigenic exposure is
10

11. retained for a longer period of time and produces a
secondary type of reaction when it meets same antigen.
(Active immunity is more effective and confers better
protection than passive immunization).
Passive Immunity:
The resistance that is transmitted in a readymade form
is known as passive immunity.
The host immune system plays no role in providing
protection. The antigenic stimulus is absent, instead,
preformed antibodies are administration. Unlike active
immunity, the latent period is absent. The immune actions
begins almost immediately and the negative phase is absent.
The immune reaction is transient and lasts for few
weeks to months. This protection is seen till the passively
administered antibodies are metabolized and eliminated from
the body. No secondary type of reaction is seen. Instead if
the same antibody is given again for the second time it is
eliminated more rapidly from the body when compared to
first time. This factor of immune elimination limits the
usefulness of passive immunity.
11

12. The passive immunity is therefore less useful than
active immunity in providing immune capacity. The only
advantage being its immediate action.
Active Immunity Classification:
Active immunity may be:
- Natural
- Artificial
Natural active immunity results from either clinical or
inapparent infection from a parasite.
A person who has recovered from these infections
develops natural active immunity. Example, a person
recovered from small pox, chicken pox etc.
Increased resistance to poliomyelitis in individuals of
developing countries due to many subclinical attacks by
poliovirys in childhood.
Some viral infections may give life long immunity
(measles).
The period of natural active immunity varies from the
type of pathogen and virulence of pathogens. Some viral
infections like common cold due to influenza virus may give
12

13. only a shorter period of immunity. The common cold due to
influenza virus may recur due to reduction in immune
response to second infection.
The immunity following bacterial infection is less
permanent when compared to viral infection some infections
like typhoid fever provide sufficient immunity for a longer
period of time.
A special type of immunity called premunition is seen
in syphilis. This is characterized by presence of immunity to
a pathogen is seen as long as the original infection is active.
Once the original infection is cured, the person becomes
susceptible to infection by the same microorganisms again.
Artificial Active Immunity:
Immunity in children includes involves both natural
active immunity and artificial active immunity.
The artificial active immunity is the immunity or
resistance induced by vaccine. Vaccine are the preparations
of live or killed microorganisms or their products used for
immunization.
13

14. The vaccine therefore are divided in to:
1. Live vaccine Bacterial
Viral
2. Killed Bacterial
Viral
3. Bacterial products divided vaccine – toxoids for
diphtheria and tetanus.
Live vaccines initiate on infection without causing any
injury or disease. The immunity following live vaccine
administration is similar to that following natural infection
but is of a lower order.
Once set, the immunity lasts for several years, but
booster doses are / may be necessary.
The administration of live vaccine in children /adults
may be done orally, (example – sabin vaccine and
poliomyelitis or parentrally. Example, Smallpox virus
vaccine.
Killed vaccine are generally less immunigenic than live
vaccine and the protection by them lasts only for a shorter
period of time. Therefore they require to be administered
repeatedly, usually at least two times. The first injection is
14

15. known as primary dose and second dose is known as booster
dose.
killed vaccine can be again given either orally (taboral
vaccine for typhoid) or parenterally. The oral route is
generally not as effective as by parental route.
The killed vaccine by parental route generally provide
humoral antibody response.
Not all the organisms are available in avirulent form.
In order to overcome this if living organisms are to be
present in vaccine (live vaccine) they have to be treated in
such a way that the organisms loose their disease producing
ability. This process is called as attenuation.
The commonly used methods for this include adopting
the organisms to unusual environmental condition so that
they lose the ability to replicate completely in their usual
host. Culturing the viruses at a temperature lower than
normal is the next method.
Live attenuated vaccine provoke a rapid protective
response through stimulation of interfering production.
Live vaccine are difficult and expensive to prepare,
possibility of dangerous extraneous organisms is also seen.
15

16. Natural Passive Immunity:
Natural passive immunity is the resistance passively
transferred from the mother to infant /baby. In humans
maternal antibodies are predominantly transferred through
placenta (especially IgG) and gives immunity to the infant,
human chelostrum is rich in IgA and also contribute for
immunity of the featus. From about 12th
week of I.U. the
human embryo starts developing IgM in its body. But the
IgM embryo at this stage is not active enough to combat all
the infections.
It is only at about after 3 months post anterior life the
infant gets immune capacity independently. Till then the
child utilizes immune system of mother that is transmitted to
it.
The transmission of antibodies from maternal to factal
circulation across placenta is an active process and it is
found that fectus has more concentration of antibodies than
maternal circulation protection so afforded is sufficient to
resist all infections during that period. Hence any infections
are more common after 3 months of age.
16

17. By active immunization of a pregnant women it is
possible to improve the passive immunity in infants.
The recommendation of titanus tunoid vaccine
prophylactically is hence of use in areus with increased
tendency for neonatal titanus.
Artificial Passive Immunity:
Artificial passive immunity is the resistance passively
transferred to a recipient by injecting antibodies. The agents
used for this purpose are hyper immune animal and human
sera, convalescent sera, and pooled human gamma globulin.
The oldest and commonest method employed is to inject
hyper immune horse sera. It is prepared by injecting
appropriate antigen into horse serum.
Example – Anti-tetanus serum (ATS) used for
prophylaxis against tetanus infection is prepared by
administering a series of doses of antigens into horse
circulation. Then the blood is collected and serum is
separated from blood. The antibodies are then concentrated
and purified and sterilized.
The main problem with animal enzymatic preparations
is an increased tendency for hypersensitivity reactions.
17

18. In order to overcome this problem human sera can be
utilized.
Serum collected from patients convalescing from
infections diseases contain high concentration of specific
antibodies. Such convulsing serum is utilized for passive
immunization against viral infections like measles and
rubella.
The main risk of using human sera is transmission of
serum hepatitis.
Passive immunization is utilized mainly for providing
immediate and temporary protection in a non immune host
having chances of infection. It is also utilized to provide
resistance till active immunization is in action.
Passive immunization can also be employed with active
immunization and this is called as “combined immunization”.
Combined immunization is indicated whenever an immediate
action is required which is given by passive immunization.
The immune actions remains active after words by active
immunization.
Paediatric or childhood is the best age at which
majority of disease can be prevented by means of various
18

19. methods. Vaccination in childhood has become an
inexpensive and most useful methods by which prophylaxis
can be given.
Since the time of introduction of vaccine there is a
decline or reduction in the overall rates of infections like
cholera, tuberculosis, typhoid, mumps, smallpox, tetanus and
polio etc. which are most common diseases affecting in early
childhood.
Some of the diseases against which the immunization
by vaccines is available at present are:
1. Diseases that can be prevented by environmental
improvement or vaccination:
- Japanese encephalitis.
- TB.
- Yellow fever.
- Typhoid.
- Rubis
- Cholera
- Hepatitis B (Horizontal transmission).
2. Diseases preventable only by vaccination:
- Poliomyelitis.
- Diphthories.
- Measles.
- Rubella.
19

20. - Mumps.
- Purtysis.
- Meningococcal meningities.
- Influenza.
- Chickenpox.
- S.pneumonia pneumonia.
- Hepatitis B (vertical transmission).
Routine Vs Special Immunization:
Based on prevalence and severity of a disease, safe and
vaccine are preferred for routine repeated administration in
infants and early childhood. Thus in India routine
administration is recommended for:
- Measles.
- Diphthoria.
- Tetanus.
- Purtusis.
- Typhoid fever and
- Tb
Robis vaccine is usually given as a post exposure
prophylaxis and in more prone individuals as a pre exposure
prophylaxis cholera vaccine is recommended only as a
measure against epidemics.
In pediatric practice immunization should be given to
all susceptible individuals and this vaccine is usually taken
20

21. at an individual level. Immunization can safely be given in
minor illness like diahhroea, URTI etc.
In order to control the vaccine preventable disease
WHO and member countries including India has established
on expanded programme on immunization.
Some of the Practical Aspects
1. There is no contraindication for concurrent
administration of multiple vaccines like DPT, OPU, or
MMR.
2. A lapse in schedule of immunization does not always
necessitate reinstitution of total course. If a second
hours of DPT or OPU is missed it is not necessary to
reinstitute the complete course.
3. If immunization scheme of a child is unknown there is
no harm in giving appropriate vaccines again.
4. Dose reduction is not appropriate since it may cause in
appropriate immunologic response, increased dose is
also not indicated which may cause side effects.
5. Live vaccines of all types and BCG should not be given
in individuals with congenital disorders of immune
21

22. system. These should also be avoided in children who
are taking steroids for rt since these causes
immunodepression. A short course of low dose of
steroids is not a contraindication for vaccines.
Vaccines of this kind should also be avoided in
children with active symptoms of AIDS.
6. Children suffering from neurologic disorders or with
previous history of convulsions are at a higher risk for
purtuse vaccine.
7. Active immunization after exposure to disease is
indicated in:
- Rabies.
- Measles (within 3 days of exposure).
- Hepatitis and
- Tetanus.
Immunization schedule:
Various immunization schedules are recommended in
order to protect a child from infections. Some of the
immunization schedules are:
22

23. National Immunization schedule :
The first visit may be made when the child is 6 weeks
old. The recommended schedule is given in next page.
Beneficiaries Age Vaccine
No. of
doses
Route of
administration
Infants
6 weeks
to 9
months
DPT
POLIO
BCG
3
3
1*
Im
Oral
Intradermal
9-12
months
Measles Subcutaneous
Children
16-24
months
DPT
Polio
1*
1**
Im
Oral
5-6
years
DT
Typhoid
1@
2
Im
Subcutaneous
10 years
Tetanus
tonoid
Typhoid
1@
1@
Im
Subcutaneous
16 years
Tetanus T
Typhoid
1@
1@
SC
SC
Pregnant
women
16-36
months
T-T 1@ Im
* For institutional deliveries BCG should be given at birth.
** Booster dose
@ 2 doses if not vaccinated
1 Intervals between two doses should not be less than one
month
2 minor illness is not a contraindication.
23

24. WHO EPI schedule
This strongly recommended institution of BCG and
polio vaccines at birth or at the time of initial contact, in
countries where Tb and polio have not been controlled. In all
countries immunization for polio is safely started at 6 weeks
of age along with DPT.
The given schedule is as follows:
Age Vaccine
Birth BCG, oral polio
6 weeks DPT, oral polio
10 weeks DPT, oral polio
14 weeks DPT, oral polio
9 months Measles
Diphtheria:
Common disease in India, which has sufficient number
of antibodies circulating in maternal circulation. The
antibodies are easily to crossed across placenta and fetal
immunity is cortered till birth and for first 3 months.
The vaccine is given as a triple vaccine DPT or D.T.
24

25. Primary dose consists of 3 doses at 4, 6 and 8 weeks of
birth, I booster dose is given during second year of age, at
18 months. A second booster dose is given at 5 years of life.
Pertusis:
- Given as triple vaccine DPT.
- Since protective antibodies cannot cross placenta
vaccination is a must.
- 3 doses are recommended at 9-8 weeks of internal from
1-3 months of age.
- Common adv reactions:
o Local pain irritability.
o Screming for a prolonged time.
o Convulsions in some cases.
- Not recommended in neuromuscular disorder and
patients with convulsive history.
Tetanus:
- Neonatal tetanus is an important cause of mortality in
many developing countries.
25

26. - Since there is no natural immunity, the unimmunized
mothers fail to transfer the antibodies to their infants
against tetanus toxin.
- Immunizing pregnant women with T toxoid of great
value.
- Vaccination against TT is given as DPT or DT or TT
alone.
- Booster dose is given at 18 months, 5 years and 10
years and thereafter 6 months intervals.
BCG:
- Bacillus culmette guerin is an attenuated strain of
mucobacterium tuberculosis. It is a line vaccine.
- In order to maintain its potency the vaccine is supplied
at a temperature of 4°C at which the potency remains
satisfactory for several months.
Since no immunity is transferred from mother to infant
BCG has to be administered after birth. The vaccine is given
intradermally above the deltoid muscle. After 2-3 weeks a
papule develops at the site of injection which ultimately
heals by scarring.
26

27. Adverse reaction being
- Regional lymphnods with infrequent dressing.
Measles:
- Live attenuated measles virus is used as a vaccine.
- Vaccine stored at 4-8°C can be used for 1 year.
- Given by S.C. or Im route.
- Recommended minimum age is nine months. Because
before this period maternal antibodies circulating in
fetal blood neutralizes the virus in live vaccine.
Mumps:
- Vaccine consists of live attenuated mumps.
- Given as a trivalent vaccine with measles and rybella.
- Mumps vaccine of MMP may be given after 12-15
months of age.
Rubella:
- Immunization is given solely to prevent congenital
rubella.
- Two approaches are recommended.
o Either to selectively immunize girls.
o Immunize girls and boys simultaneously.
27

28. - In India incidence of rubella is not known.
- Prophylaxis starts at on age of 12 months.
Rabies:
- Cause (explain).
- Since the incubation period is more post exposure
vaccination is safely given for infected individual.
- It employs administration of killed rabies virus
vaccine.
- Modified semple’s vaccine is one vaccin for rabies
administered S.C. over anterior abdominal wall for 7-
14 days. In some cases booster doses are also required.
- Modern vaccine have advantage over semples vaccines
in that no neurological symptoms are seen.
- These vaccine are given Im or Sc on 0, 3, 7, 14, 30 and
90 days.
Typhoid:
- Employs standard acetone killed salmonelle typhi
infections.
28

29. - Primary immunization requires two S.C. doses at 4
week intervals. In out breaks the period may be
reduced to 1 week also.
- Dose is 5ml for children of 10 years.
- Booster doses once in 3 years are recommended.
Cholera:
- Suspension of heat killed vibrio cholera is used as
vaccine for cholera.
- Recommended rarely and only in outbreaks of the
disease.
- Given either ID, Im or Scly.
Hepatitis B
A purified suspension of 22 nanometer particles
bearing H.B. virus surface antigens found in some chronic
carriers are used as vaccines. Any residual virus is
inactivated by formaldehyde and heat.
Recently a genetically engineered recombinant vaccine
is available.
In pediatrics its main use is in preventing mother to
transmit the disease to infant neonates borned to carrier
29

30. mothers should given Human anti hepatitis B globulin
(AHBG) and a course of vaccines according to
recommendation by manufacturers.
30