VACCINATION
Assist Prof Dr
Syed Yousaf Kazmi
OBJECTIVES
 Explain active and passive immunity
 Define & explain basic concepts and
mechanisms of protection
 Classify common vaccines
 List common vaccine preventable diseases
 Discuss immunization program
ACTIVE IMMUNITY
 Active immunity is induced after




contact with foreign antigens
Clinical or subclinical infection,
immunization, exposure to
microbial products (e.g., toxins,
toxoids),
Host actively produces antibodies,
lymphocytes- ability to respond to
the antigens
Adv: Long term protection
Disadv: Slow onset
Innate & adaptive immunity
PASSIVE IMMUNITY
 Antibodies produced in another
host
 Passive administration of
antibody against certain viruses
(e.g. Hepatitis B) -limit viral
multiplication after needle prick
 Adv: Preformed antibodies is
promptly available in large
amounts
 Disadv: short life span of these
antibodies and possible
hypersensitivity to foreign Ig
MECHANISMS OF
PROTECTION
 Immunization is an Artificial Adaptive Response
to an antigen
 May be Active or Passive
 In Active Artificial Response-Antigen used in the
forms of Live Attenuated pathogen (bacterium,
virus etc.), Killed whole cell, Microbial extract,
Vaccine conjugate
 In Passive Artificial Response-Preformed
immunoglobulins from other species are
administered

MECHANISM OF PROTECTIONACTIVE IMMUNIZATION
 Aim is to generate Primary
Adaptive Immune response &
Memory B/T cells
 Future exposure to a
microorganism/ toxin etc. will
elicit a secondary Adaptive
Immune response due to Memory
Cells
 A rapid and higher Antibody
response is elicited
 Protection is achieved
MECHANISM OF PROTECTIONACTIVE IMMUNIZATION
CELLULAR RESPONSE IN
IMMUNIZATION
 All intracellular microbes e.g. virus,
Mycobacterium tuberculosis elicit Cellular
Adaptive response (Cytotoxic T cells)
 Immunization by Live/ attenuated viruses-cell
mediated response-Memory T cells
 Subsequent exposure to virus/ intracellular
microbe-lysis of infected cell
HUMORAL RESPONSE IN
IMMUNIZATION



Soluble antigens/ vaccine conjugates elicit Humoral
response
Secondary immune response is produced due to
activation of memory B cells-antibody produced
Neutralization of pathogen/ toxin etc.
CLASSIFICATION OF
VACCINES
1. LIVE VACCINES
 Attenuated living microbes
 Replicate in host-elicit immune






response without causing disease
More robust and long-lasting immune
response with single dose
Chance to revert to virulent form
Require cold chain for survival
Contraindicated in
immunocompromised/ Pregnancy
Polio, Rubella, Mumps, Typhoid fever
Cell mediated immunity
CLASSIFICATION OF
VACCINES
2. INACTIVATED VACCINES
 Cannot replicate in host
 Safe in immunocompromised/
pregnancy
 Mount weak immune response
 Multiple doses (booster) for
protection
 Mainly Humoral immunity
 Whole cell & Fractional vaccine
INACTIVATED VACCINE
A. Whole Cell Vaccine
a. Bacteria (Pertussis, Typhoid, Cholera, Plague)
b. Viruses (Polio, Hepatitis A, Rabies, Influenza)
B. Fractional Vaccine
a. Subunit Protein Based (Hepatitis B, acellular
pertussis, Influenza, Anthrax)
b. Toxoid (Diphtheria, Tetanus)
c. Polysaccharide Vaccines
a. Pure ( Salmonella Vi, Pneumococcal)
b. Conjugate ( Hib, Pneumococcal)
LIST OF COMMON VACCINE
PREVENTABLE DISEASES
Diphtheria, Haemophilus
Influenzae serotype b,
Hepatitis B, Measles,
Meningitis, Mumps,
Pertussis, Poliomyelitis,
Rubella
Tetanus, Tuberculosis,
Yellow fever, Influenza,
Pneumococcal
pneumonia
IMMUNIZATION PROGRAM
THANK YOU
ANY QUESTION