Topic 17   Vaccines

Introduction

Immunology began as attempts were made to develop ways of protecting people and animals from infectious disease.  It was from such attempts that researchers eventually learned about the  existence of the immune system and realized that immunity was the best way of protection. Vaccination is one of the major contributions of immunology to medical science.

To induce immunity against a specific infectious agent, an individual is immunized against it, either actively or passively.  In active immunization, the individual is exposed to the causative agent or parts thereof; in passive immunization, the individual receives protective molecules or cells produced in another individual.  The effort spent protecting human populations from communicable diseases has been highly successful.  The widespread use if immunoprophylaxis has led to the global eradication of one disease (smallpox) and the near elimination of several other diseases in other countries (poliomyelitis, rubella, tetanus, diphtheria, and measles in the developed countries).  Unfortunately, because of economic or scientific obstacles, vaccines are either nonexistent or not readily available for several diseases associated with significant rates of morbidity or mortality.  Recent advances in immunology have led to the development of new and promising vaccine strategies.  This section focuses on some of the existing vaccine strategies as well as on some experimental designs that may become the vaccines of the future.

 

Objectives

On completion of this section and the required readings, you should be able to:

n  compare the acquisition of passive and active immunization and give specific examples of each;

n  discuss the recommended program for Childhood immunizations;

n  construct a table to compare the advantages and disadvantages of attenuated vs inactivated vaccines;

n  compare the risks associated with attenuated or inactivated vaccines vs specific purified macromolecular vaccines;

n  compare the three general forms of purified macromolecular vaccines; polysaccharide, toxoid, and recombinant antigens;

n  draw a diagram to show the steps in the production of a vaccina vector vaccine;

n  draw a diagram to show the uses of an anti-idiotype antibody as a vaccine;

n  discuss the advantages of anti-idiotype vaccines;

n  compare solid matrix antibody-antigen complexes with immunostimulating complexes in the development of multivalent subunit vaccines.

Required Reading

Refer to the Textbook Key for the appropriate readings for this section.

 

P Key Words

•    passive immunization

•    active immunization

•    vaccine

•    boosters

•    herd immunity

•    attenuated vaccines

•    inactivated vaccines

•    reversion toxoid

•    vector

•    vector vaccines

•    anti-idiotype vaccine

•    Immunostimulating Complexes (ISCOMS)

•    Solid matric antibody antigens (SMAA)

P Key Concepts

n  Protective immunity can be induced by either active or passive immunization procedures

n  Active immunization may result from a previous infection or from vaccination, while passive immunization may occur by natural means, such as the transfer of antibodies from mother to fetus via the placenta, or to an infant via the colostrum; or by artificial means such as by the administration of immune globulins.

n  Three types of vaccines are currently used in humans: attenuated (avirulent) microorganisms, inactivated (killed) microorganisms, or purified macromolecules.

n  Vaccines containing modified live organisms generally produce better immunity than do vaccines containing inactivated organisms but are potentially more hazardous.

n  New techniques for producing antigen such as recombinant DNA techniques or use of synthetic antigens have lead to the development of several new or improved vaccines attenuated vaccines

DID YOU KNOW?

The Eradication of Smallpox

The story of eradication of smallpox is one of the most uplifting stories in human history.  It illustrates what can be done when humanitarian instincts are allowed to flourish.  The eradication of smallpox required the tireless and devoted efforts of a vast army of public-health workers in numerous countries throughout the world.  Smallpox was a disease admirably suited for control by vaccination.  By the middle of the 20th century, smallpox vaccination was completely routine in most of the developed countries of the developed world.  Control of the disease in such countries by vaccination and quarantine had shown what could be done if sufficient will were exercised.  In most Western countries, immigration authorities insisted that travelers show evidence of smallpox vaccination in order to be admitted to the country.  School children were routinely vaccinated, and the disease only arose if an isolated population, unvaccinated perhaps for religious reasons, became infected by the introduction into such a population of an isolated infected individual.  Such incidents were so rare as to be newsworthy.

In the underdeveloped parts of the world the situation was quite different.  Smallpox was endemic and infected individuals might be found anywhere.  Because the smallpox vaccine was so highly effective and so easily administered, an eradication campaign could be considered.  All that would be necessary would be sufficient money for personnel, travel and supplies.  Considering the amount of money spent by countries on military matters, the cost of the eradication program was quite modest.  With the eradication of the disease, the smallpox vaccination will no longer be required, nor will international certificates of small pox vaccination.  Apart from the alleviation of human suffering, the savings have already repaid the small investment many times over.

The techniques used to contain and eradicate smallpox could, perhaps, be applied to other diseases, but with no other disease will success be so likely.  The severity of smallpox, the effectiveness of the vaccine, its ease of administration and the characteristic symptoms that can be recognized even by someone without formal medical training make smallpox a unique case.  For most diseases that are common in the Third World, we would probably be satisfied with a drastic reduction in incidence rather that complete eradication.

D.A.  Henderson. The Eradication of Smallpox.  In: Microorganisms From Smallpox to Lyme Disease. Reading from Scientific American.  Edited by:

T.D. Brock.  W.H. Freeman and Company, New York, 1990

Review Questions

1. Textbook Study Questions

Review questions at the end of the Chapter 18.  The answers with explanations are available at the end of the textbook.

2.  Multiple Choice Questions

1.  The best way to provide immunologic protection against tetanus neonatorum (of the newborn) is to:

A) inject the infant with human tetanus antitoxin

B)  inject the newborn with tetanus toxoid

C)  inject the mother with toxoid within 72 hours of the birth of her child

D) immunize the mother with tetanus toxoid before or early in pregnancy

E)  give the child antitoxin and toxoid for both passive and active immunization.

 

2.  The administration of vaccines is not without hazard.  Of the following, which is least likely to affect adversely an immunocompromised host?

A) measles vaccine

B)  pneumococcal vaccine

C)  bacille Calmette-Guerin

D) mumps vaccine

E)  Sabin poliomyelitis vaccine

3.  The pneumococcal polysaccharide vaccine should be administered to all except:

A) individuals with chronic cardiorespiratory disease

B)  elderly (over 60 years of age) persons

C)  children (under 2 years of age)

D) persons with chronic renal failure

E)  individuals with sickle cell disease

4.  The major disadvantage of passive immunization is that it

A) is ineffective

B)  is expensive

C)  is liable to cause serum sickens

D) interferes with active immunization

E)  induces short-lived immunity

5.  One of the most potent adjuvants known is called

A) alum

B)  saponin

C)  Freund’s complete adjuvant

D) liposomes

E)  endotoxin

3. Definitions/short Answer Questions

1.  Differentiate between variolation and vaccination.

2.  Define vaccine.

3.  Name four types of vaccines and give examples of each.

4.  Explain why are influenza vaccines so relatively ineffective.  How might you begin to improve on current influenza vaccine

5.  How would you manufacture immune globulin against rattlesnake venom?

6.  Why do we use adjuvants?  What sort of adjuvants would you recommend for routine use in a vaccine to be administered to children?  What side effects might you anticipate from their use?