A quick Glimpse…

Principles Underlying Vaccination

• Concept of Immunity
• Self vs. Non-self
• Antigen specificity
• Indicated by presence of effector cells
• Protection from infectious diseases using above methods

Vaccinations

• Boosters (multiple inoculations) are required
• Interference of passive maternal antibodies

Effectiveness of Vaccinations

• Small percentage of recipients will respond poorly
• Role of genetic determinants
• Herd Immunity
• Majority of population is immune, so chance of susceptible individual contacting infected individual is low
• Measles Epidemic

Herd Immunity

• Factors affecting herd immunity
• Environmental Factors: crowded conditions, seasonal variations
• Strength of Individual’s Immune System
• Infectiousness of Disease: greater the risk of infection, the higher percentage of people need vaccines to attain herd immunity
• When enough people are vaccinated, chance of germ infecting the non-immunized population is small
• Can lead to disappearance of diseases (smallpox)
• Vaccination no longer necessary

Quantitative Data

Further Proof of the Effectiveness of Vaccines

Development of Vaccines

• Common misconception that activation of the immune system results in protective immunity
• Multiple factors affect decisions when making vaccines
• 1. Activation of specific branch of immune system
• 2. Development of immunological memory

Role of Memory Cells

• Depends on incubation period of pathogen
• Short Incubation Periods
• ex. Influenza
• Symptoms already under way by the time memory cells are activated
• Repeated immunizations with neutralizing antibodies
• Long Incubation Periods
• ex. Poliovirus
• Enough time to allow memory B cells to respond