Acquired Immunity
Artificial Natural
Active Passive Active Passive
Subclinical Trans-
Toxoid Homologous
Infection placental
Clinical
Live Vacc Heterologous
Infection
Killed vacc
IMMUNITY
Immunity refers to the ability of the human body
to resist disease agents and their toxins through
possession of antibodies.
Ab Titre
20 40 60
Days After First Injection
THE IMMUNE RESPONSE:
When an antigen (Ag) is introduced into the human body, it
stimulates the production of antibodies (Ab). Micro-organisms
(and their toxins) and vaccines are antigens which evoke an
immune response. The immune response is two types:-
1) The primary response: when an Ag is introduced into the
body for the first time, there is a latent period of 3-10 days
before Abs appear in the blood. A peak is quickly reached and
the level of Abs gradually falls over a period of weeks or
months.
2) The secondary (booster) response: the
response to a booster dose of the same Ag
differs in a number of ways from the primary
response:
- has a shorter latent period and more rapid
production of Abs.
- Abs are produced in abundance and a
high level is maintained for a longer period.
- the Abs produced tend to have a greater
capacity to bind to the Ags.
The accelerated response is attributed to the
immunological memory.
THE IMMUNE SYSTEM:
A. Humoral Immunity:
This type of immunity is due to circulating Abs (Gamma -
globulin's also called immunoglobulins).
It is a major defense against bacterial infections.
On stimulation, B-lymphocytes divide and its daughter
cells are transformed into plasma-cells.
The latter secrete the Abs into the circulation.
The types of immunoglobulins are:
(i) IgG: Most Abs to infection belong to this class.
It is widely distributed in the tissue fluids and are equally
available in the intra and extravascular spaces.
It can cross the placenta, and so it provides passive immunity
to the newborn.
(ii) IgM: This is the first type produced by the maturing
foetus, and it is the main type responsible for the primary
immune response.
It is mainly intravascular but it does not cross the placenta.
(iii) IgA: Found in high concentration in the external
secretions: Colostrum, Saliva, tears and intestinal
and bronchial secretions. Because of this, IgA is part
of the first line of defence against infectious agents.
(iv) IgE: Very low in serum and tissue fluids. It has a
particular affinity to fix to tissues and so it is able to
sensitize mast cells so that upon contact with Ags,
the biologically active material present in mast cells is
released. Because of this it is called a "reagin".
v) Igd: Ab-activity has rarely been demonstrated,
and the biologic function is uncertain.
B. CELLULAR IMMUNITY:
Another way of establishing host resistance is through
T-lymphocytes.
These cells synthesize and release pharmacologically
active substances ("lymphokines") which can kill
cells carrying foreign Ags.
T-lymphocytes also act against the invader by
stimulation of macrophages.
This activity of the immune system is known as cell
mediated immunity. The peak of activity occurs
around the tenth day.
Rechallenge by a subsequent infection evokes a
secondary response more rapid and of greater
intensity.
This type of immunity is responsible for intracellular
infection (due to viruses and some bacteria e.g.
Tubercle bacilli) and fungal infection.
Besides infection, cellular immunity is responsible for
delayed hypersensitivity reactions, lysis of tumor
cells and rejection of tissue or organ transplants.
C. The complement system:
All vertebrates possess in their serum certain
proteins and other factors which participate in
the immune response.
Complements facilitate the Ağ-AB reactions.
D. Enzymes effect systems
which serve to control clotting, laying down of
fibrin and dilatation of local capillaries to
facilitate passage of WBCs.
When functioning efficiently, the body is usually
well protected by its immune defenses. There
are situations in which production of immunity is
depressed. Examples are:-
Congenital and acquired immune-deficiencies.
Certain infections like mumps and measles.
Presence of passive immunity (maternal Abs).
Treatment with immuno suppressive drugs (e.g.
steroids)
Malnutrition
Diabetes mellitus
Old age
IMMUNIZATION
Vaccination and Immunization
These terms are often used interchangeably.
Vaccination and vaccine derive from vaccinia, the virus once
used as smallpox vaccine.
Thus, vaccination originally meant inoculation with vaccinia
virus to render a person immune to smallpox.
Although some persons still prefer that vaccination be
restricted to this use, most use it to denote the
administration of any vaccine or toxoid.
Immunization is more inclusive term denoting the process of
inducing or providing immunity artificially. Immunization
can be active or passive.
Infectious diseases can be prevented by stimulating the
individual to develop an active immunologic defence in
preparation for meeting the challenge of future natural
exposure (active immunization) or by supplying preformed
human or animal antibody to individuals already exposed
or about to be exposed, to certain infectious agents
(passive immunization).
In 1979G/1399H the vaccination against certain
childhood diseases became obligatory secondary to
the issue of a Royal Decree which dictated the
sustain of birth certificates until the completion of the
primary series of vaccination against:
T.B., Diphtheria, Tetanus neonatorum, whooping
cough, measles, and poliomyelitis.
Latter on the list included coverage against mumps,
rubella , hepatitis B viral infections and hib. .
In 1991G/1411H a change in the schedule of vaccine
administration was implemented (table 1), and
continued until the a subsequent schedule of
vaccination was approved and implemented in
Shawal 17th 1422H/January 1st 2002. The most
recent schedule is applied starting Jan. 2008.
The changes included in the new vaccination schedule
reflect the efforts of continuous monitoring and
evaluation of the previous system.
It depended largely on the incidence of certain diseases
and their impact.
It also followed the most recent developments in the
manufacturing and industry of vaccines internationally
employed.
National and local studies and continuous research in the field of
immunizable childhood diseases had a great influence and
impact. The scientific recommendation of including:
- the haemophilus influenza – b vaccine (Hib) to the previous
schedule was supported by a Royal approval.
[The use of adjuvant vaccines for the first time in Saudi Arabia
was a real achievement in this field (DPT + Hib)].
- IPV has been recommended for the first time since ever.
- Hepatitis A ,and Varicella vaccines have been recently added.
- Measles (mono) vaccine has been indicated at an earlier age.
-The two MMR doses are partially considered as boosters to
measles vaccine. (see the attached schedule).
The routine schedules for active immunization of
normal infants and children, and of children not
immunized in early infancy have recently been
revised by the immunization Practices Advisory
Committee, Ministry of Health.
The birth certificate will not be issued until the child
has completed the recommended primary
immunization of infancy period including ( MMR,
Varicella and OPV ) at 12 months of age.
Active immunization involves administration of all or part of a
microorganism or a modified product of that microorganism
(e.g. toxoid) to evoke an immunologic response that
provides partial or complete protection to the recipient.
Vaccines incorporating an intact agent may be either live
(usually attenuated) or killed (inactivated).
The current available routine schedule for active immunization
in Saudi Arabia has been revised and implemented starting
January 2008 (Table 3).
The types and routes of administration of various vaccines are
shown in (Table 4).
Schedule for Immunization
Several factors influence recommendations
concerning the age at which vaccines are
administered.
a. They are age-specific risks of diseases.
b. They are age-specific risks of complications.
c. Ability of persons of a given age to respond
to the vaccine(s).
d. Potential interference with the immune
response by maternal antibodies (measles).
Modification of the recommended schedule may be
necessary because of missed appointment or
intercurrent illness.
Interruption of a recommended series does not require
starting the series over again or adding extra doses,
regardless of the interval elapsed.
If a dose of DPT or OPV is missed, immunization should
occur on the next visit as if the usual interval had
elapsed.
In contrast, giving doses of a vaccine or toxoid at less
than recommended intervals may lessen the antibody
response and therefore should be avoided.
Doses given at less than recommended intervals should
not be counted as part of a primary series.
Some vaccines produce local or systemic symptoms in
certain recipients when given too frequently (e.g., Td,
DT, and rabies).
Such reactions are thought to result from the formation
of antigen-antibody complexes.
* Td = Adult tetanus toxoid (full dose) and diphtheria
toxoid (reduced dose) for adult use.
* DT = Diphtheria and tetanus toxoids for use in children
aged < 7 years old.
Table 1: Routine immunization schedule for normal infants and children in
Saudi Arabia applied 1991.
Recommen Vaccine(s)** Comments
ded Age
Birth BCG, HBV
6 weeks DTP, OPV, DTP and OPV can be initiated as age 2 wk
HBV during epidemics.
3 months DTP, OPV
5 months DTP, OPV
6 months HBV, Measles Completion of primary series of DTP and OPV.
Completion of HBV series.
12 months MMR Should not be given before 12 months of age.
18 months DTP, OPV First booster dose of DTP and OPV
4-6 years DTP, OPV Second booster dose of DTP and OPV;
preferably at or before school entry.
* This schedule for active immunization has been recommended by the
Immunization Practices Advisory Committee, Ministry of Health in 1991.
Table (2): Recent schedule for Vaccination of Newborns in Saudi Arabia.( Jan. 2002-Jan.2008)
Visit No. Age Vaccines **(dose)
• BCG
First At birth
• HBV(1)
• DPT(1)
Second At two months
• OPV(1)
• Hib(1)
• HBV
• DPT(2)
Third At four months
• OPV(2)
• Hib(2)
• DPT(3)
Fourth End of sixth months
• OPV(3)
• Hib(3)
• HBV(3)
• MMR(1)
Fifth End of 12 months
• DPT (Booster1)
Sixth End of 18 months
• OPV (Booster1)
• Hib (Booster1)
• DPT (Booster2)
Seventh At school entry 4-6 years
• OPVBooster2)
• MMR (Booster2)
* The DPT + Hib vaccine is a tetraimmune adjuvant vaccine that has been introduced
for the first time in Saudi Arabia in 2002 and is given in one injectable dose.
Table (3): Recent schedule for Vaccination of Newborns in Saudi Arabia. Starting January 2008.
Age at visit Vaccines
• BCG
At birth
• HepB
• IPV
2 - Months
• [ DTP, HepB , Hib ]
• OPV
4 - Months
• [ DTP, HepB, Hib ]
• OPV,
6 - Months
• [ DTP, HepB , Hib ]
• Measles ( mono )
9 - Months
• OPV ,MMR
12 - Months
• Varicella
• OPV
18 - Months
• DTP, Hib
• Hepatitis (A)
24 - Months
• Hepatitis (A)
4 - 6 Years
• OPV,DTP, MMR, Varicella.
Table 4: Certain available vaccines and their routes of administration.
Vaccine Type Route
Intradermal (preferred) or
BCG Live Bacteria subcutaneous
Intramuscular
DTP D&T = Toxoids
P = inactivated bacteria
Hepatitis B(HBV) Inactivated viral antigen Intramuscular
Haemophilus Polysaccharide Intramuscular
Influenza b
(Hib)
Subcutaneous
MMR Live attenuated viruses
Oral
OPV Live attenuated virus
BCG = Bacillus Calmette – Guerin vaccine (tuberculosis).
DPT = Diphtheria, pertussis and tetanus vaccine.
MMR = Live measles, mumps and rubella viruses in a combined vaccine.
OPV = Oral Poliovirus vaccines containing attenuated poliovirus types 1,2 and 3.
The Cold Chain
Failure of a vaccine to protect an individual child
may be due to a number of reasons.
* The vaccine may no longer be "antigenic" so
that it does not stimulate the body to produce
antibodies.
* With "live vaccines", which can occur if the
vaccine is no longer alive.
* Most live vaccines are killed easily by changes
of temperature, such as might occur if they are
left out of the refrigerator for a long time.
(This is particularly true of measles vaccine).
** Vaccines must be kept constantly cold throughout the chain of
storage and transport which they have to pass through before
reaching the child.
Breaks in this "cold chain", as it has come to be called, may be
due to a batch of vaccine delivery to a Ministry of Health depot
or to a hospital or health centre.
It can happen as a result of the breakdown of the refrigerating
system. Great care must be taken to try to avoid this
happening, and it is always better to have a refrigerator which
can run on two different sources of power.
Live vaccines are also damaged by sunlight, which is especially
likely to happen after they have been prepared (reconstituted)
for injection in the clinic or at the school.
Vaccines should always be kept in the shade.
They can also be affected by detergents or
antiseptics in syringes which have not been
properly cleaned or rinsed.
Even in the best circumstances, vaccines
eventually lose their power and it is very
important to look at the date of expiry on the
container.
(This is the date after which the manufactures
cannot guarantee the power of the vaccine).
The chances that such expired vaccines will fail to
protect increase the longer the interval after the expiry
date.
Live vaccines for injection should be used on the same
day that they are reconstituted for injection, that is,
after the water (diluent) has been added.
Oral poliomyelitis vaccine can be used after opening
until the vial is all used up, so long as it is returned
to the refrigerator after clinic and kept in the shade.
The End
Thank You