The scientific basis of vaccines Flashcards
1
Q
What was variolation?
A
- If someone had smallpox you would scrape the lesions after they had healed, and then inoculated it on someone else’s arm - theory is that it would protect them
- Didnt work every time, lots of people died because of it
2
Q
What were the 4 scientific principles from Jenner’s experiments?
A
- Challenge dose - proves protection from infection
- Concept of attenuation
- Concept that prior exposure to antigen boosts protective response
- Cross-species protection - antigenic similarity
3
Q
How did we manage to eradicate smallpox?
A
- Had good vaccination programmes that worked, with good case finding surveillance and restriction of movement of sufferers
- With smallpox there are no subclinical infections (either get it or dont)
- Also no latency of the virus
- There is no animal reservoir, so once you got rid of it in humans, you were good
- Had an effective vaccine
- Has slow spread and poor transmission
4
Q
Define vaccine
A
- Material from an organism that will actively enhance adaptive immunity
- Produces an immunologically ‘primed’ state that allows for a rapid second immune response on exposure to antigen
- Antibodies and/or T cells
5
Q
What vaccine ‘scares’ have we had?
A
MMR and autsm
Whooping cough
6
Q
What is the vaccine paradox?
A
- Herd immunity
- Our immune memory is boosted by periodic outbreaks of disease in community and vaccines
- As disease rates decline due to vaccination, no-one gets the disease and so there is no natural immune boosting against the disease
- This increases the importance of vaccination uptake
7
Q
What are the different types of immunity?
A
- Active immunity = innate/adaptive. Natural exposure, infection and vaccination - gives long effect
- Passive immunity = antibody from another source such as serum. Used for prophylaxis and/or treatment - short effect
8
Q
What are the general principles of vaccines?
A
- Induce the correct type of response (antibodies -> polio, cell-mediated -> TB)
- Induce the response in the right place (mucosal- sIgA -> flu, polio; systemic -> yellow fever)
- Duration of protection - short term -> travel; long-term -> memory essential; booster -> natural or vaccines
9
Q
What is haemophilus influenza?
A
- Paediatric disease - usually 6 months-3yrs
- Initially a nasopharyngitis that spreads to an otitis media, sinusitis, bronchitis, pneumonia or sometime epiglottis
- Spreads and causes bacteraemia, septic arthritis, meningitis in 60% of cases
- Most haemophilus infections occur in the first few months, howeber we dont start to make Abs until about 2, so need to give vaccine early
10
Q
What is the problem with giving live vaccines to infants?
A
- Maternal in neonate and sIgA in milk
- If you give a live attenuated vaccine, the virus would be neutralised by maternal Ab - giving no protection
11
Q
What are the different routes of inoculation?
A
- Oral - e.g. polio
- Intradermal - BCG
- Deep s/c or i/m - most
12
Q
What are the advantages of oral administration of vaccines?
A
- Avoids needles and so risk of HIV/HepB
- mimicry of natural route of infection
- ensures exposure to large immune surface
- Good sIgA response
- Humoral immunity via lymphocyte trafficking to other mucosal surfaces
13
Q
What is the main problem with oral vaccines?
A
was it swallowed?!
14
Q
Monotypic vs polytypic ags
A
- Measles virus doesnt change very much - doesnt mutate rapidly or express a range of Ags on the surface - tend to only get it once = MONOTYPIC
- However other pathogens are changing all the time, such as flu and gonorrhoea = POLYTYPIC
15
Q
What are the different types of vaccines?
A
- Live, attenuated
- Killed, whole organism
- Sub-unit vaccines
