2. Vaccination vs immunization
• ‘Vaccination’ is a process of inoculating the
vaccine/antigen in to the body.
• The vaccinee may or may not seroconvert
• The process of inducing immune response,
which can be ‘humoral’ or ‘cell-mediated’ in
the vaccinee is called ‘immunization’.
7. Humoral vs cell mediated immunity
• Vaccines confer protection against diseases by
inducing both antibodies and T-cells.
• Antibodies are of several different types (IgG,
IgM, IgA, IgD and IgE) and they differ in their
structure, half life, site of action and mechanism
of action.
• Humoral immunity is the principal defence
mechanism against extracellular microbes and
their toxins.
• B lymphocytes secrete antibodies that act by
neutralization, complement activation or by
promoting opsono- phagocytosis.
8.
9. • Cell mediated immunity (CMI) is the principal
defence mechanism against intracellular
microbes.
• The effectors of CMI, the T cells are of two
types.
• The helper T cells secrete cytokines that
stimulate the proliferation and differentiation
of T cells as well as other cells including B
lymphocytes, macrophages and NK cells.
• The cytotoxic T cells act by lysing infected
cells.
10.
11. VACCINES
• Live vaccines are attenuated (modified) live
organisms, which have immunogenicity i.e. can
generate antibodies, but have lost pathogenicity
i.e. capability to cause disease.
• Efficiently trigger the activation of both innate
and adaptive immune system.
• Toll-like receptors (TLRs) - single membrane-
spanning non-catalytic receptors that recognize
structurally conserved molecules derived from
microbes.
• Pattern is very similar to natural infection
12. Inactivated vaccines may consist of
• whole inactivated organisms like whole cell
pertussis, typhoid, rabies, inactivated polio
• modified exotoxins called ‘toxoids’ like diphtheria
toxoid or tetanus toxoid
• subunits like polysaccharide antigens of
salmonella typhi, Hemophilus influenzae type-B
(Hib), and surface proteins of hepatitis B
Conjugation of the polysaccharide with a protein
carrier significantly improves the immune
response
13. T CELL DEPENDENCY
• Protein antigens stimulate both B and T cells, while
polysaccharides stimulate only B cells.
• Accordingly called T cell dependent and independent
antigens
• Proteins or conjugated polysaccharide – taken up by
APC, activate follicular dendritic cells (FDC) present in
germinal centre. Required for massive clonal
proliferation, class switch in immunoglobulins, affinity
maturation.
• Results in plasma cells that deposit in niches of bome
marrow and provide long lasting immunity.
• Generation of memory B cells – follow rapid kinetics
during second exposure
14. • Polysaccharide vaccines – fail to recruit helper T
cells. Results in plasma cells that persists till
dissolution of germinal centres. Decline in
antibody levels after dissolution of GC.
• Subsequent exposure – same kinetics
• Hyporesponsiveness - revaccination with PS may
indude lower Ab responses. Esp seen with
menigococci and pneumococci. Hence
recommended only single booster even for
lifelong immunity.
• PS are unable to evoke response in < 2 yrs –
immaturity of marginal zone.
15.
16.
17. Vaccination schedules
• Interval b/w doses 0-1-6 more immunogenic.
• Interval b/w primary doses – 4 weeks
• Interval b/w primary and booster – min 4
months
18. • Young age immunization problems – maternal
antibodies and immature immune system.
• Strategies followed –
1. Increased no. of vaccine doses
2. Adjuvants
3. Boosters at later age
• Early, accelerated schedules are practiced in
developing countries
19. • Adjuvants: Adjuvants are potentiating agents
and immunostimulants.
• Simultaneous administration of adjuvant –
potentiate immune response both humoral and
CMI.
Classic – mineral oil suspension, alluminium
salts
Newly developed – liposomes, immune
stimulating complex, squalene complex,
bordetella, vit A, beryllium salts, toxic salts of
silica.
20. • Direct increase in number of cells which
involved in antibody production.
• Ensuring effective processing of antibody.
• Prolonging the duration of antigen
• Increasing the synthesis and release of
antibody from antibody forming cells.
21. • Rationale for Hep B/ BCG/ OPV @ birth
Although maternal antibodies interfere with the
induction of infant antibody responses, they
may allow a certain degree of priming, i.e. of
induction of memory B cells – hence Hep B
Maternal Abs don’t interfere with T cell
responses – hence BCG. Sometimes enhance
also.
No maternal IgA in the gut to neutralize the
virus – hence OPV
22. BASIC TERMINOLOGIES
• Basic reproductive no.(Ro) – measures avg no.
of secondary cases generated by 1 primary
case in a susceptible population.
Ro < 1 , disease is declining (herd effect)
Ro > 1 , outbreak is occuring
• Immunogenecity – ability of vaccine to induce
antibodies.
23. • Vaccine efficacy – ability to protect an
individual. Assessed by clinical trials, cohort
studies or case control studies.
VE = ARU – ARV * 100
ARU
• Vaccine effectiveness – ability to protect
community. Sum of vaccine efficacy and herd
effect. Revealed after vaccine is introduced
into program.
24. • Herd immunity – denotes resistance of a
population to the spread of vaccine preventable
diseases where causative organisms spread from
human to human.
• Proportion immune in a herd
• Herd effect –protection offered to unvaccinated
members when good proportion (usually more
than 85%) of the herd is vaccinated.
• Due to reduced carriage of the causative
microorganism by the vaccinated cohort and thus
is seen only with vaccines against those diseases
where humans are the only source
25.
26. • Contact immunity – vaccinated individual can
pass on vaccine to another individual
• Unique property of some vaccines
• Herd immunity vs contact immunity
• Virtually by breaking the transmission of the
infection or lessening the chances of
susceptible individuals coming in contact with
infective individual.
• Clinical practice - contact immunity does not
play significant role, while herd protection
plays a major role
27. General recommendations
• Ideal immunization schedule
epidemiologicaly relevant,
immunologicaly competent,
technologicaly feasible,
socially acceptable,
affordable and sustainable
28. • Number of doses
Live vaccines induce immunity with a single
dose; inactivated vaccines require multiple
doses (initial doses to prime and later doses to
boost)
Multiple doses of OPV – reduced take up of virus
29. • Vaccination schedules in developing
countries:
6, 10, 14 weeks e.g. India, Kenya, Madagascar,
Mozambique, Philippines,
2, 4, 6 months e.g. Egypt, Chile, Mexico,
Thailand, Uruguay, Argentina, Brazil
2, 3, 4 months e.g. Gambia, Indonesia, Turkey,
Vietnam
2, 3, 5 months e.g. Malaysia
3, 4, 5 months e.g. China
30. • age of administration of vaccines
Nature of the vaccine- killed, live,
polysaccharide
Age and immune status of the recipient i.e
ability of persons of a certain age to respond
to the vaccine and potential interference with
the immune response by passively transferred
maternal antibody or previously administered
antibody containing blood products.
Age-specific risks for disease, age specific risks
for complications.
31. • IAPCOI has categorized vaccines into four categories:
Vaccines covered under Expanded Program on Immunization
(EPI):
BCG, OPV, DTwP, Measles, DT, TT, Hep B, MMR, Hib
Vaccines recommended by IAP in addition to EPI vaccines:
Typhoid, IPV, Tdap, Td, HPV
Vaccines which are to be given after one-to-one discussion with
the parents: Hepatitis A, PCV13, Chicken Pox, DTaP, Rotavirus
Vaccines to be given in special circumstances:
Rabies, Influenza, PPV23, Japanese encephalitis,
Meningococcal.
32. Practice of vaccination
• Safe injection practices
Hands should be washed with soap and water or
cleaned with an alcohol based hand rub
Skin at the injection site should be prepared with
70% isopropyl alcohol or another disinfecting
agent and allowed to dry before injection.
Separate disposable syringes and needles should be
used for each injection.
Pre-filling of syringe should be avoided as most
vaccines appear similar and administration error
can occur.
33. • Instructions for injectables
To prevent accidental needle-sticks or reuse, a needle
should not be recapped after use.
Disposable needles and syringes should be discarded
promptly in puncture-proof, labeled containers.
Changing needles between drawing vaccine into the
syringe and injecting it into the child is not necessary.
Different vaccines should not be mixed in the same
syringe unless specifically licensed and labeled for such
use.
Whenever possible, patients should be observed for an
allergic reaction for 15 to 20 minutes after receiving
immunization.
34. • Instructions for oral
Vaccine must be swallowed and retained. OPV
should be repeated immediately if a child spits it
out, fails to swallow, or regurgitates a dose within
10 minutes after administration.
If the second dose is not retained, neither dose
should be counted, and vaccine should be re-
administered.
Breastfeeding does not interfere with successful
immunization with oral vaccines (e.g., OPV,
Rotavirus).
Regarding rotavirus vaccines, instructions given by
the manufacturer should be followed if the child
spits out the vaccine.
35. • Site and route of administration
Preferred site is anterolateral aspect of upper
thigh or deltoid area of upper arm
Upper outer quadrant of buttocks not
recommended
Distance separating the 2 injections is arbitrary
but should be at least 1 inch so that local
reactions are unlikely to overlap
“Aspiration” by gently pulling back – no
recommendations
36.
37.
38.
39. Other recommendations
• Vaccines which contain stabiliser and
preservative generally cause local reaction like
pain and swelling. Hence administered IM
• All injections meant for SC can be safely given IM
not vice versa
• Antibody-containing products and inactivated
antigen can be administered simultaneously at
different sites or at any time interval between
doses. Non simultaneous administration can also
be done at any interval.
40. • Antibody containing products and live antigen
should not be administered simultaneously.
Antibody containing products can be
administered after 2 weeks of live antigen
without any interference with seroconversion.
• Measles and varicella containing vaccines
should be administered 3-6 months after
immunoglobulins or blood transfusion
41. • Vaccines in bleeding disorders – Unless
contraindicated, subcutaneous route should
be used. For those vaccines (aluminium
adjuvanted) which need to be given only IM,
vaccination should be planned after factor
replacement.
• Tuberculin skin test – same visit during which
live viral vaccines, such as MMR, Measles,
Varicella
• Otherwise Tuberculin testing should be
postponed for 4 to 6 weeks
42. Contraindications and Precautions
• Contraindication – condition in recipient
increases chances of serious adverse reaction
Severe anaphylaxis, acute encephalopathy, SCID
Temporary – pregnancy, immunosuppression
Vaccines should not be administered.
43. • Precaution – condition in recipient increases
chances of adverse reaction or might
compromise ability to induce immunity.
High grade fever, persistent cry, seizures within 3
days.
Vaccines should be deferred.
44. REFERENCES
• Immunization in clinical practice – Naveen
Thaker
• Partha’s immunization digest
• FAQ on immunization practices – Vipin
Vashistha
