A quick Glimpse…

Immunological Memory vs. Serum Antibody Levels

Types of Vaccines

• Whole-Organism
• Attenuated Viral/Bacterial
• Inactivated Viral/Bacterial
• Purified Macromolecules
• Polysaccharide
• Toxoid
• Recombinant Antigen
• Recombinant-Vector
• DNA
• Synthetic Peptide
• Multivalent Subunit

Whole-Organism Vaccines

• Many common vaccines used consist of inactivated or attenuated bacterial cells or viral particles
• Includes attenuated and inactivated vaccines

Attenuated Viral or Bacterial Vaccines

• Attenuation – to reduce in force, value, amount, or degree; weaken
• Achieved by growth under abnormal culture conditions
• Bacillus Calmette-Guerin (BCG)
• Act as a double edged sword, as they have distinct advantages and disadvantages…

Advantages of Attenuated Bacterial or Viral Vaccines

• Advantages stem from their capacity for transient growth
• Prolonged immune-system exposure
• Single immunizations
• Replication within host cells

Exception to the Rule…

• Sabin Polio vaccine consists of 3 attenuated strains of poliovirus
• Colonization of intestine results in immunity to all 3 strains
• Production of secretory IgA and induction of IgM and IgG
• Result is the need for boosters
• Individual strains interfere with one another
• First immunization  one strain predominates in growth
• Second Immunization  immunity generated by previous immunization limits growth of previously predominant strain
• Third Immunization  same principle as second immunization

Disadvantages of Attenuated Bacterial or Viral Vaccines

• MAJOR disadvantage is possible reversion
• ex: Rate of reversion of Sabin Polio vaccine is one case in 4 million doses
• Presence of other viruses as contaminants
• Unforeseen postvaccine complications