Scientific Basis of Vaccines Flashcards
(56 cards)
What is variolation?
Variolation (with variola minor) and Vaccination (vaccinia) - taking scabs from mild disease and inoculating people
What are the scientific principles learnt about vaccines from Jenner’s experiments?
- Challenge dose – proves protection from infection
- Concept of attenuation
- Concept that prior exposure to agent boosts protective response
- Cross-species protection – antigenic similarity
How was smallpox eradicated?
- Vaccination programmes
- case finding (surveillance)
- and movement control
Why was smallpox eradication possible?
- No subclinical infections (mild / full blown)
- After recovery, the virus was eliminated - no carrier states
- No animal reservoir
- Effective vaccine (live vaccinia virus)
- Slow spread, poor transmission
What is a vaccine?
Material from an organism that will actively enhance adaptive immunity
How do vaccines provide immunity?
Produces an immunologically “primed” state that allows for a rapid secondary immune response on exposure to antigen - drives T cell memory
What is the role of vaccines?
Prevention of DISEASE not infection
- can’t stop people getting infected but can stop disease symptoms occurring
How do we achieve long lasting immunity with vaccines?
Long lasting - requires immunological memory
Antibodies and/or T cells (humoral and cell mediated immunity)
What are the aims of vaccines?
- Protection of the individual: ↓rate/severity
- Protection of the population: Herd Immunity
- Eradication of disease
What factors determine eradication of a disease?
Eradication requires balance between the epidemic risk to individuals and a population
What is the am of the rubella vaccine?
Rubella: a mild disease. Aim is to prevent congenital damage, not protect population
How is immunity memory maintained?
Herd Immunity memory boosted by periodic outbreaks of disease in community and vaccines
Why are booster vaccines required?
As disease rates decline - no natural boosting
Increases importance of vaccination uptake rates
Outline the risks and benefits of vaccination against measles
Infection Complications
- 1/15 pneumonia, otitis media, bronchitis
- 1/5000 encephalitis (15% mortality)
Vaccination Damage
- 1/1000 fever/convulsions
- 1/400,000 meningo encephalitis
What are the risks and benefits of vaccinating against diphtheria?
Infection Complications
- 5% mortality
Vaccination Damage
- Occasional swelling
Outline the risks and benefits of the whooping cough vaccination
Infection Complications
- 0.1% mortality
- frequent pneumonia
Vaccination Damage
- 1 / 600,000 encephalopathy
What are the different types of active immunity?
- Innate / Adaptive (Cell Mediated Immunity; antibodies)
- Natural exposure (carriage)
- Infection
- Vaccination
Long effect
What are the different types of passive immunity?
Antibody from another source: serum
- Prophylaxis and/or treatment
Short effect
Describe the primary immune response to antigens
Primary exposure 5-7 days → antibody response
2 weeks for a full response
- IgM to IgG switching
- memory B and T cells
How long does a secondary immune response last?
Secondary response 2 days for full protective response (prior exposure)
How do we remain protected against pathogens after exposure?
Post-exposure immunoprotection due to response vs specific antigens
e. g. surface proteins, polysaccharides, toxins
- good targets for vaccine candidates
What are the general principles of vaccines?
- Induce correct TYPE of response
- antibodies / cell mediated - Induce response in RIGHT PLACE
- mucosal sIgA / systemic - Duration of protection
- Age of vaccination
Why are antibody vaccines insufficient for systemic infections?
Antibodies aren’t sufficient for systemic infections as they can’t enter host cells or viruses
What are the different durations of vaccines?
Short-term (travel) antibody sufficient
Long-term memory essential
Boosters - natural (seasonal epidemics; carriage)
- vaccines
