1. Basic Concepts in Immunity
Antibodies
Protein substances or
Globulins derived from
B and T lymphocytes
Formed by the body as a defensive response
Titers (concentrations) can be measured to specific antigens
Antigen
Foreign substance or seen by the body as foreign
Stimulates antibody production

2. Host Defense Mechanisms
Active Immunity (natural and artificial)
Body produces antibodies in reaction to antigen (e.g. natural~acquired, and artificial~vaccinations)
Typically takes 2-3 weeks to confer immunity
Passive Immunity (natural and artificial)
“borrowed” in 3 ways:
Injection of serum with antibodies produced by another host (e.g., immunoglobulin)
Placental transfer (short-term immunity)
Breastfeeding
Immunity is immediate

3. Herd Immunity
Resistance of group or population to spread of specific disease through group
Resistance due to high proportion of population immune to disease (usually due to previous immunization or infection)
Theoretically, when 85-90% of population is immune, herd immunity should protect other %
However localized outbreak could occur if not well distributed

4. Source: JHSPH Open CourseWare. Fundamentals of Epidemiology

5. Carrier of Communicable Disease
Harbors infectious agent
Asymptomatic
No overt signs or symptoms
Can be transmitted to others
Can be carriers during incubation period or for long periods of time (chronic carriers)
“Typhoid Mary”
Typhoid Mary –
In the early 1900’s, Mary Mallon was a cook for a family in Long Island. 5 living in house contracted typhoid fever. Family commissioned George Soper, sanitary engineer from NYC Heatlh Dept. He suspected Mary who disappeared to NYC even though she had no S&S. She threatened him when he wanted to test her for disease. He looked into her work history and found that 7 of 8 families for whom she had worked contracted the disease. A 1903 epidemic in Ithaca which infected 1300 people was thought to have originated with Mary. She was teken kicking and screaming to be tested in NY. Although she had no visible S&S, she was found to have the bacteria that caused typhoid fever in her feces. She was given option to remove gallbladder to end carrier state, but she refused. They sent her to an isolation cottage on N. Brother Island in NY. She was released after 3 years due to public outcry. Conditions of her release included staying in contact with public health officials and not working in food handling profession. She changed her name and was found several years later working as cook in Maternity hospital in NYC where several more cases were attributed to her. She was arrested and taken back to the isolation cottage for the remainder of her life. She lived to be 70 years of age.
Sometimes can’t only look for people with obvious S&S of disease

6. Vaccination Active immunity produced by vaccine
Immunity and immunologic memory similar to natural infection but without risk of disease

7. Classification of Vaccines
Live attenuated
viral
bacterial
Inactivated

8. Whole Fractional Inactivated Vaccines viruses bacteria protein-based
toxoid
subunit
polysaccharide-based
pure
conjugate
Fractional

9. Principles of Vaccination
General Rule
The more similar a vaccine is to the disease-causing form of the organism, the better the immune response to the vaccine

10. Live Attenuated Vaccines
Attenuated (weakened) form of the "wild" virus or bacterium
Must replicate to be effective
Immune response similar to natural infection
Usually produce immunity with one dose*
*except those administered orally

11. Live Attenuated Vaccines
Severe reactions possible
Interference from circulating antibody
Fragile – must be stored and handled carefully

12. Live Attenuated Vaccines
Viral measles, mumps, rubella, varicella/zoster, yellow fever, rotavirus, intranasal influenza, rotavirus, vaccinia
Bacterial BCG, oral typhoid

13. Inactivated Vaccines Cannot replicate
Generally not as effective as live vaccines
Less interference from circulating antibody than live vaccines
Generally require 3-5 doses
Immune response mostly humoral
Antibody titer may diminish with time

14. Whole-cell vaccines Inactivated Vaccines
Viral polio, hepatitis A, rabies, influenza*
Bacterial pertussis*, typhoid* cholera*, plague*
Whole-cell vaccines
*not available in the United States

15. Fractional vaccines Inactivated Vaccines
Subunit hepatitis B, influenza, acellular pertussis, human papillomavirus, anthrax
Toxoid diphtheria, tetanus
Fractional vaccines