Vaccines

Question 1

Which disease is completely irradicated by vaccine?

Answer 1

Smallpox (in 1979)

99.9% of measles

Almost all of Hib and epiglottitis

Question 2

Why do we immunise people?

Answer 2

To prevent infection
To treat infection (especially rabies or diphtheria if given vaccine within 24 hours)
To prevent/treat non-infectious diseases like cancer (HPV, HepB)
To modify immune responses (can desensitise people to Allergy by introducing small doses OR give Ab to make disease less severe e.g. in measles)

Question 3

What is passive immunisation?

Answer 3

Where human, horse or Mab’s are used to treat or prevent disease. There are two types: (1) pooled: where Ab is derived from plasma or (2) hyperimmune: where those with plasma of high dose Ab or infect animals and derive high doses of Ab

Question 4

T/F: Passive immunisation is long lived

Answer 4

FALSE. It is short lived and potentially hazardous because can deliver active T cells

Question 5

What is active immunisation?

Answer 5

Where the body makes its own immune response to the infectious agent. This may be to a living organism or to parts of the capsule/virion etc.

Question 6

List some mechanisms of use for active immunisation using living organisms

Answer 6

These can be living unattenuated, that is from a different host or route E.g.;

1) use of cowpox to treat small pox
2) Adenovirus to treat respiratory infections when given by mouth it wont have diarrhoeal side effect

Emperically attenuated: Become less virulent (BCG vaccine for m.TB), Typhoid, Polio (Oral phase vaccine), MMR, VZV, yellow fever

Rationally attenuated: Deletion of toxin genes (cholera)

Reassortment: Clone genes for adhesins and add to an existing vaccine (Rotateq - Rotavirus dsRNA and Influenza ssRNA virus segmented genome against Ha and NA)

Antigen expressed on living vector

Question 7

List some mechanisms of use for active immunisation using particles of organisms

Answer 7

1) Inactivated vaccine: Polio (Salk: injected/killed vaccine), Influenza, HepA, Japanese encephalitis, rabies, Cholera, Typhoid, Pertussus
2) Purified product (+/- modification): HepB surface antigen, HPV uses virus like particles, acellular pertussis (that includes the toxin, filamentous HA and pertactin), TOXOIDS (those that have A-B toxin e.g. cholera, diptheria, tetanus), Cellular polysaccharides (unmodified; Salmonella typhi, pneumococcal polyvalent vaccine OR conjugated; Hib and meningococcal)
3) Product of cloned gene
4) synthetic Ig; peptide vaccine
5) DNA vaccine (experimental only)

Question 8

What are some advantages for living vaccines?

Answer 8

More natural better immune response
Local immunity
Ease of administration

Question 9

What are some disadvantages for living vaccines?

Answer 9

Can sometimes revert back to virulent form (e.g. WT Polio)
Cannot use in immunocompromised (get sick) or pregnant women (affect foetus)
May be contaminated: cannot sterilise so other organisms may grow in vaccine
Need to be transported by “cold-chain” to keep the organism alive
May fail due to preexisting immunity or IFN interference

Question 10

What are some advantages of killed vaccines?

Answer 10

They are stable
Unlikely to be contaminated
Cannot spread
Safe for immunocompromised

Question 11

What are some disadvantages for killed vaccines?

Answer 11

There is a weaker immune response
High dises required
Need adjuvant
They are expensive