1. Vaccines

2. Herd Immunity
HERD IMMUNITY: presence of immunity in MOST of the population – inability of an infectious disease to spread in a population because of the lack of a critical concentration of non-immune hosts (Resistance of a population to infection and to spread of an infectious organism because of the immunity of a large percentage of the population)
Level can be altered by introduction of new susceptible individuals into population
Level can be altered by changes in pathogen
Antigenic shift – major change in antigenic character of pathogen

3. Some Examples of Emerging and Reemerging Infectious Diseases
Some examples of emerging and reemerging infectious diseases. Although disease such as HIV are indicated in only one or two significant locations, they are very widespread and a threat in many regions.
Emerging and Reemerging Infectious Diseases and Pathogens = New, reemerging or drug-resistant infections whose incidence in humans has increased within the past three decades or whose incidence threatens to increase in the near future

4. Some Reasons for Increases in Emerging and Reemerging Infectious Diseases
Crowding (population growth)
Habitat disruption (urbanization)
Increased international travel, migration
Increased worldwide transport
Changes in food processing, handling, agricultural practices
Changes in human behavior
Changes in ecology and climate
Modern medicine (ex. immunosuppression; excessive or inappropriate antibiotic use)
Inadequacy of public infrastructure and vaccination programs
Bioterrorism

5. How to Control the Spread of Diseases
Control the reservoir (i.e. control at the source)
Animal → immunization or slaughter
Ex. Immunize cattle against E. coli O157 to prevent entry of the bacteria into the human food chain
Human → isolate infected host (prevent contact)
Prompt diagnosis & treatment of infected hosts
Try to identify & treat carriers (difficult to do)
Environment → de-contaminate or avoid contact

6. Control the Susceptible Population
Control transmission
Remove vectors (ex. pesticide control of insects)
Prevent contamination of fomites (ex. use disinfectants)
Chlorination of water supplies
Pasteurization of milk
Supervision and inspection of food and food handlers
Cover your sneeze, wash your hands, etc.
Control the Susceptible Population
Promote healthy lifestyle (hygiene, nutrition, etc.)
Avoid high-risk behaviors
Use vaccine (if available)
Raise herd immunity

7. Establish a “Disease Control Network”
Network of individuals and organizations who identify, track, and control infectious diseases
Health care workers
Epidemiologists
Diagnostic labs
Local, national, and international public health organizations

8. Five public health practices that have had the greatest success in decreasing the incidence of infectious diseases:
1. Ensuring a clean water supply
2. Ensuring a clean food supply
3. Promoting personal cleanliness and hygiene
4. Controlling insect vectors
5. Public education campaigns focused on STD’s and respiratory diseases
→ On average, incidence of infectious diseases and mortality due to microbial pathogens have declined greatly in last 100 years (due to more effective control practices, better diagnosis, better drugs, etc.)

9. VACCINATION (immunization): intentional administration of a harmless or less harmful form of a pathogen to induce a specific immune response that protects the individual against later exposure to the same pathogen
VACCINE: Preparation of microbial antigens used to induce protective immunity
May consist of killed, living, weakened (attenuated) microbes or inactivated bacterial toxins (toxoids), purified cell material, recombinant vectors or DNA
Vaccines attempt to induce antibodies and activated T cells to protect host from future infection
End march 23

10. Vaccination is a medical miracle

11. Active Immunity: Whole Agent Vaccines:
Vaccine induces immune response in host that will not result in disease (recipient makes own antibodies)
Whole Agent Vaccines:
Contain whole, nonvirulent microorganisms
Killed or attenuated (weakened) microorganisms
Subunit Vaccines:
Contain some part or product of the microorganism that can induce an immune response in the recipient
Forms of subunit vaccines
capsular polysaccharides
recombinant surface antigens
inactivated exotoxins (toxoids)

12. DNA Vaccines
DNA directly introduced into host cell via air pressure or gene gun
When injected into muscle cells, DNA taken into nucleus and pathogen’s DNA fragment is expressed
Host immune system responds to foreign proteins produced
Many DNA vaccine trials are currently being run

14. Adjuvants
An adjuvant is a chemical substance that can be added to a vaccine in order to enhance the immune response to the vaccine.
Alum or Freud’s