Passive & Active Immunization: Immunity via Antibodies & Vaccines, Summaries of Microbiology

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ACTIVE AND PASSIVE IMMUNIZATION

SOS In Microbiology

M.Sc 2nd^ Semester

Paper: Immunology (202)

Unit -5 (1)

Introduction

• The incidence of diseases such as diphtheria, measles, mumps, pertussis (whooping cough), rubella (German measles), poliomyelitis, and tetanus has declined dramatically as vaccination has become more common.
• Clearly, vaccination is a cost-effective weapon for disease prevention.
• Immunity to infectious microorganisms can be achieved by active or passive immunization.
• In each case, immunity can be acquired either by

1. Natural processes (usually by transfer from mother to fetus or by previous infection by the organism)
2. Artificial means such as injection of antibodies or Vaccines.

• The agents used for inducing passive immunity include antibodies from humans or animals in active immunization is achieved by inoculation with microbial pathogens that induce immunity but do not cause disease or with antigenic components from the pathogens.

B. Passive immunization can also be achieved artificially by injecting a recipient with preformed antibodies.

• Passive immunization provided a major defense against various infectious diseases in past days.

Conditions that warrant the use of passive immunization-

1. Deficiency in synthesis of antibody as a result of Congenital or acquired B-cell defects, alone or together with other immunodeficiency.
2. Exposure or likely exposure to a disease that will cause complications (e.g., a child with leukemia exposed to varicella or measles), or when time does not permit adequate protection by active immunization.

3. Infection by pathogens whose effects may be ameliorated by antibody. For example, if individuals who have not received up- to-date active immunization against tetanus suffer a puncture wound, they are given an injection of horse antiserum to tetanus toxin. The preformed horse antibody neutralizes any tetanus toxin produced by Clostridium tetani in the wound.

 Conditions when use Passive immunization-Botulism, tetanus, diphtheria, hepatitis, measles, and rabies, as well agisnt poisonous snake and insect bites.

 To travelers or health-care workers who will soon be exposed to an infectious organism and lack active immunity to it.

 Passive immunization does not activate the immune system, it generates no memory response and the protection provided is transient.

B. Active Immunization

 The goal of active immunization is to elicit protective immunity and immunologic memory.

 A successful active immunization elicits a heightened immune response after subsequent exposure to the pathogenic agent which help to eliminates the pathogen or prevents disease mediated by its products.

Active immunization can be achieved by

A. Natural infection with a microorganism,

B. Acquired artificially by administration of a vaccine.

 In active immunization, the immune system plays an active role—proliferation of antigen-reactive T and B cells results in the formation of memory cells.

 Vaccination of children is begun at about 2 months of age.

 The recommended program of childhood immunizations by the American Academy of Pediatrics, includes the following vaccines:

• Hepatitis B vaccine
• Diphtheria-pertussis (acellular)-tetanus (DPaT) combined vaccine
• Inactivated (Salk) polio vaccine (IPV); the oral (Sabin) (vaccine is no longer recommended for use in the United States)
• Measles-mumps-rubella (MMR) combined vaccine
• Haemophilus influenzae (Hib) vaccine
• Varicella zoster (Var) vaccine for chickenpox
• Pneumococcal conjugate vaccine (PCV); a new addition to the list.

 In addition, hepatitis A vaccine at 18 months and influenza vaccines after 6 months are recommended for infants in high-risk populations.

 Polio vaccine are Multiple immunizations to ensure that an

adequate immune response is generated to each of the three

strains of poliovirus that make up the vaccine.

 Recommendations for vaccination of adults depend on the risk

group. Vaccines for meningitis, pneumonia, and influenza are

often given to groups living in close quarters (e.g., military

recruits) or to individuals with reduced immunity (e.g., the

elderly).

 Vaccination is not 100% effective. With any vaccine, a small

percentage of recipients will respond poorly and therefore will

not be adequately protected.

 This is not a serious problem if the majority of the population

is immune to an infectious agent. In this case, the chance of a

susceptible individual contacting an infected individual is so

low that the susceptible one is not likely to become infected.

This phenomenon is known as herd immunity. 10

Herd immunity- It is the indirect protection from a

contagious infectious disease that happens when a

population is immune either through vaccination or

immunity developed through previous infection.

• This means that even people who are not vaccinated, or in

whom the vaccine doesn’t trigger immunity, are protected

because people around them who are immune can act as

buffers between them and an infected person.

• Once herd immunity has been established for a while, and

the ability of the disease to spread is hindered, the disease

can eventually be eleminated.