Vaccinations

Question 1

What are the goals of vaccination?

Answer 1

-generate long-lasting, protective immunity
-eradicate disease
-reduce spread of disease

Question 2

What factors favour a disease being eradicated?

Answer 2

-disease limited to humans (can’t reinvade from animal host)
-no long term carrier state in humans
-few unrecognised clinical cases (surveillance possible)
-one/few serotypes (groups w/antigens) (only one vaccine needed)
-vaccine can be cheap, stable and effective

Question 3

What is herd immunity?

Answer 3

when most of the population is immunised against a disease, the disease spread is constrained and unlikely to spread
-% pop needed for herd immunity depends on how easily transmitted disease is
-for person-to-person diseases

Question 4

How do vaccines work?

Answer 4

induce antibodies

Question 5

What are features of effective vaccinations?

Answer 5

-safe
-protective (protection that lasts!)
-induces neutralising antibodies
-induces cytotoxic T cells (cell-mediated responses)
-practicalities: cost, administration, few side effects, biological stability

Question 6

What are the main types of vaccinations?

Answer 6

living
-attenuated pathogens (virulence reduced)
non-living
-killed pathogens (pathogen can’t replicate)
-pathogen subunit (molecular component)

Question 7

How can pathogens be attenuated for vaccines?

Answer 7

-genetic manipulation
-adapt pathogens for low temperatures
-serial passage (changing environment pathogen is growing in so it becomes less adapted to original host)

Question 8

Why are attenuated vaccines generally more effective than non-living vaccines?

Answer 8

recognised by body as “real” infection so induces appropriate immune response

Question 9

How can pathogens be killed for vaccines?

Answer 9

inactivation using chemical treatment, heat, etc

Question 10

What subunits can be used in subunit vaccines?

Answer 10

-toxoids (chemically inactivated toxins)
-recombinant proteins
-subcellular fractions (separated component of bact)
-conjugate vaccines (carrier protein carries polysaccharide component)
-virus-like particles

Question 11

What are recombinant vector vaccines?

Answer 11

vectors genetically engineered to express pathogen antigen in host
eg. AstraZeneca SARS-COV2 vaccine

Question 12

What are DNA/RNA vaccines?

Answer 12

vaccines which use DNA/RNA to transiently express pathogen antigen in host cell
-typically mRNA surrounded by lipid coat
eg. Pfizer and Moderna SARS-COV2 vaccines

Question 13

What are the advantages of living (attenuated) vaccines?

Answer 13

-immunity lasts years
-only require 1 dose
-low cost
-can be administrated naturally
-no adjuvant required

Question 14

What are the disadvantages of living (attenuated) vaccines?

Answer 14

-attenuation not always possible
-not as safe -may revert back to being virulent; not suitable for immunocompromised
-needs cold storage

Question 15

What are the advantages of non-living (killed or subunit) vaccines?

Answer 15

-safe and suitable for immunocompromised
-not heat liable (can be used in tropical countries!)

Question 16

What are the disadvantages of non-living (killed or subunit) vaccines?

Answer 16

-often require multiple doses, which must be done by injection
-adjuvant often required (particularly for subunit vaccines)
-high cost (cost of manipulating pathogens)
-immunity not always long

Question 17

What are barriers against effective vaccinations being made for some diseases?

eg. TB, respiratory infections, HIV

Answer 17

-pathogen has complex life cycle (eg. vectors involved)
-T cell immunity required for some infections (vaccines focus on B cells)
-pathogen has high mutation rates
-multiple types of pathogen cause infection

Question 18

What prevents some people from having vaccines?

Answer 18

-personal/religious objections
-fake news and conspiracy theories
-expense, lack of medical infrastructure, etc