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1. Comunicación y Gerencia

2. Exposed host
Dr. Hanaa El-Sayed Bayomy
Assistant Professor
Community Medicine

3. Immunity (defense mechanism)
 Defense mechanism (resistance) that protect the
body from micro-organisms and potentially harmful
agents.

4. Immunity
General
(innate)
Natural
barrier
Inner body
defense
Specific
(acquired)
Natural
Passive
(maternal
immunity)
Active
(infections)
Artificially
Passive
(Seroprophylaixs
)
Active
(vaccines)

5. General defense mechanism
Natural barrier of infection:
 Skin
 Intact surface & bactericidal effect of sweat.
 Eye
 Blinking reflex & tears prevent infection
 Respiratory system
 sneezing & coughing reflexes, cilia and mucus
membrane sweep out the foreign material.
 G.I.T
 Saliva & bacterial flora of mouth inhibit growth of
microorganisms.
 Gastric acidity has Bactericidal effect.
 Intestinal flora of colon destroy microorganism .
 Vagina
 Acidity & lactobacilli inhibit growth of microorganism.

6. General defense mechanism
Inner body defense:
Plasma  lysozyme  bacterial lysis –
diluting effect.
Phagocytosis  polymorphnuclear
leucocytes (PNLS) & macrophages.

7. Specific (Acquired) Immunity
Naturally Acquired immunity
 Active natural acquired immunity :
 Subclinical infection:
Repeated attacks  immunity.
 Clinical infection: One attack of infection  different
degrees of immunity:
Absolute immunity as in yellow fever.
Solid or long lasting immunity e.g. measles, mumps,
chicken pox.
Mild or short lived immunity e.g. influenza.
Latent (persistence of dormant focus) infection 
infection immunity (premunition) e.g. T.B.

8. Specific (Acquired) Immunity
Naturally Acquired immunity:
 Passive natural acquired immunity :
 Transplacental materno- foetal immunity : (in the
last weeks of pregnancy).
 IGg  small molecules can cross the placenta .
 Give temporary immunity for 6-9 months. MMR
 No maternal acquired immunity for pertussis (IgM) or T.B
(cell mediated immunity).
 Colostrum & breast milk which contain:
 High contents of antibodies (IgA).
 Lysozyme & macrophages.

9. Artificially induced immunity

10. Passive artificially induced
immunity (Seroprophylaxis)
 Definition: Passive artificially acquired immunity, induced by
injection of already formed immunoglobulin, antibodies, and
antitoxins, and lymphocytes to induce humoral or cellular immunity.
Advantages and disadvantages:
Give rapid but temporary protection without sensitization of
memory cells.
 Used in prophylaxis or in treatment and before or after
exposure to infection.
Preparations:
Human preparations
Animal preparations

11. Human preparations
1. Normal human immunoglobulins (NHI):
 Prepared from large pool of plasma of volunteers in endemic area.
 Used in prevention of measles, polio, rubella, virus hepatitis A.
 Used for sero- prevention if given on early exposure and sero-
attenuation on late exposure e.g. measles, HBV.
2. Specific human immunoglobulins (SHI):
 Prepared from plasma of actively immunized donors or
convalescent carriers of specific infections.
 Used in prevention of viral disease as HBV, varicella zoster
infection and rabies.
Advantages:
Used in small doses, gives immediate immunity for long period (30-
50 days) Safe (does not lead to serum sickness or anaphylactic
reactions).
Disadvantages:
 relatively expensive & not constantly available.

12. Animal preparations
Anti-toxins: e.g. in seroprphylaxis or serotherapy
in Diphtheria, tetanus and gas gangrene
Given in large dose, give short protection (1-2 weeks).
May lead to severe hypersensitivity reaction (serum
sickness).

13. Active artificially acquired immunity:
(Vaccines & Toxoids)
Vaccine
Definition : They are preparations of one or
more types of organisms

14. Types of vaccines :
 Live attenuated vaccines:
 More potent than killed vaccines.
 Given for only one dose except for polio (sabin).
 Should not be given to pregnant women or persons
with immunodeficiency disease.
 Examples:
Measles, mumps, rubella (or MMR),
sabin (OPV),
BCG (T.B),
yellow fever vaccine,
otten vaccine of plague.

15. Types of vaccines :
 Killed or in activated vaccines:
 Killed by heat or chemicals .
 Require primary series of 2-3 doses and some time
booster dose.
 Given usually by intramuscular or subcutaneous
injection .
 Examples :
 Pertussis vaccine,
 DPT,
 salk of polio,
 TAB of typhoid.

16. Types of vaccines :
Polysaccharide (capsular) vaccine:
Examples :
Meningiococcal vaccine of meningitis.
Pneumococcal vaccine.
Haemophilus influenza type b vaccine.
Typhoid vaccine.

17. Types of vaccines :
 Surface antigen vaccines:
 e.g. vaccine for viral hepatitis B manufactured
by genetic engineering in the yeast cells.
 Recombinant vaccine

18. Toxoid
 Definition: detoxified toxin so as to remove its
toxicity but still regain its antigenicity.
 Examples : Diphtheria Toxoid & Tetanus Toxoid.

19. System of active immunization:
 1- Primary dose:
 Single dose only  e.g. MMR, measles, mumps, rubella,
BCG, yellow fever.
 Multiple doses : e.g. DPT, OPV, HBV, TAB, koll's.
 2- Booster dose: given after suitable period of time to
individual or group at risk to maintain satisfactory level of
immunity.

20. Route of administration of
vaccines & toxoid
 S.C or IM  for most immunizations.
 ID (intradermal)  BCG vaccine of T.B.
 Orally  sabin vaccine of polio (oral drops), oral
BCG vaccine.
 Intranasal vaccine for influenza.

21. Protective period of active
immunization:
 Months e.g. cholera vaccine  for 6 ms.
 2 years e.g. TAB vaccine for typhoid (enterica).
 3-5 years e.g. DPT, TT.
 5 years e.g. BCG vaccine.
 10 years e.g. yellow fever vaccine.
 Solid (life long) immunity e.g. measles, mumps,
rubella, MMR.

22. Effectiveness of active
immunization (protective value):
Absolute protective  yellow fever.
Almost absolute (solid)  99% e.g. MMR, small
pox vaccine, toxoid of diphtheria & tetanus, HBV
(96%).
Highly protective  80- 90 % e.g BCG, pertussis,
polio.
Moderately protective  40- 60% e.g TAB,
cholera vaccine.

23. Complications of active immunization
(Hazards or side effects):
 General reaction: as fever, malaise, headache,
body aches.
 Local reaction: pain, swelling, redness,
tenderness, abecess.
 General infection: due to contaminated syringes
e.g HIV, HBV, HCV.
 Specific hazards:
 BCG if given S.C or IM.
 Rabies vaccine especially new tissue vaccine.
 Pertussis vaccine  encephalopathy.

24. Mixed or combined vaccines:
Salk DPT (quadriple vaccine)  salk + diphtheria +
pertussis + Tetanus.
DPT  Diphtheria + pertussis + Tetanus.
DT  Diphtheria + tetanus.
MMR  Measles + mumps + Rubella.

25. Vaccines giving local immunity to
mucus membranes:
 Sabin vaccine  small intestine.
 Influenza internasal vaccine  nasal
mucosa.

26. The End
Thank You