Science of vaccination

Question 1

What are the aims of immunisation

Answer 1

To protect those at highest risk (selective immunisation strategy)
Mass vaccination: To eradicate (small pox), eliminate (polio) or contain(Hep B) disease (mass immunisation strategy)

Question 2

Give examples of selective vaccination

Answer 2

• Travel (other countries)- e.g. Typhoid
• Occupational risk- e.g. Hepatitis B
• High risk groups- e.g. Additional boosters for flu vaccine 18 to 65 yo
• Outbreak control- e.g. Hepatitis A

Question 3

What are the immune response to vaccination

Answer 3

To produce the same immune protection which usually follows natural infection but without causing disease

To generate long-lasting immunity

To interrupt spread of infection

Question 4

Describe Live vaccines and give examples

Answer 4

-Attenuated strains which replicate in host
- Attenuation means the virus or bacterium has been weakened to reduce virulence so it cannot cause disease in healthy people
- Acts like natural infection
- Live vaccines are the closest to actual infection and therefore elicit good, strong, long-lasting immune responses
Examples: MMR, BCG, yellow fever, (rotavirus, ‘Fluenz’ for children)

Question 5

explain the difference between live and inactivated vaccines

Answer 5

Live vaccines:
Induce long-lasting immunity
Strong immune response evoked
Can revert to virulence
Poor stability
Contraindications in pregnancy/ immunosuppressed
Viruses, vaccines and passive antibody can interfere

Inactivated vaccines:
Shorter lasting immunity 
Adjuvant needed
Unable to cause the infection
Stable 
Fewer Contraindications
Constituents clearly defined
Need several doses
Local reactions common

Question 6

What is herd immunity and why is it important

Answer 6

certain level of immunity in the population which protects the whole population because the pathogen stops spreading in the community.

IMPORTANT- disease can be eradicated and unvaccinated individuals are protected

Question 7

Define the reproductive ratio

Answer 7

general measure of how infectious a disease is

Question 8

what is the basic reproduction number

Answer 8

R0

Question 9

What does R0 indicate

Answer 9

R0 <1 = no sustained transmission

R0 >1= epidemic possible

Question 10

What is the herd immunity threshold/ critical vaccine threshold?

Answer 10

the number of people that NEED to be vaccinated to prevent an epidemic
Herd Immunity Threshold (HIT)
HIT= 1- (1/R0)

Question 11

List 6 vaccine preventable diseases and whether they are bacterial or viral

Answer 11

measles (virus)
polio (virus)
rubella (virus)
mumps (virus)
pertussis (bacterium)
TB (bacterium)
typhoid (bacterium)
tetanus (bacterium)

Question 12

what causes pertussis

Answer 12

Bordatella pertussis (bacterium)

Question 13

what are the complications of pertussis

Answer 13

Respiratory – the majority of cases involve some degree of collapsed lung and/or pneumonia
Neurological – lack of oxygen leading to altered consciousness, convulsions, permanent brain damage, death
Severe weight loss and dehydration due to vomiting
Sudden death - babies may stop breathing, apnoeic attacks

Question 14

Describe inactivated vaccines and give example

Answer 14

Do not contain a pathogen capable of replicating and causing disease.
Polio, rabies

Question 15

What are the types of sub-unit vaccines and give examples

Answer 15

Polysaccharide- PPV
Conjugate- PCV
Toxoid- Tetanus
Recombinant vaccine- Hep B

Question 16

What is the difference between polysaccharide and conjugate

Answer 16

Polysaccharide:
T-cell independent.
Less immunogenic in under 2s.
No booster response

Conjugate:
Designed to enhance immune response, particularly in children under 2 years old.

Question 17

Give other antibody therapies and their example

Answer 17

Human source-pooled blood preparations from donors (Hepatitis B immunoglobulin- HBIG)
Monoclonal- Palivizumab
Animal source
Diphtheria anti-toxin (used for treatment of diphtheria)

Question 18

Give pros and cons of antibodies

Answer 18

pros: rapid, preventative
cons: expensive, potential for adverse events