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Principles of Medicine (POM) - Block 3 > Lecture 20: Vaccination > Flashcards

Lecture 20: Vaccination Flashcards

1
Q

What is a vaccine?

A

Something that stimulates the immune system, without causing serious harm or side effects

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2
Q

What is the aim of immunisation?

A

To provoke immunological memory to protect individual against a particular disease if you later encounter it

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3
Q

What makes a vaccine ideal?

A
  • safe
  • easy to administer
  • single dose, needle-free
  • cheap
  • stable
  • active against all variants
  • life-long protection
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4
Q

What is significant about immune memory?

A

Movement to peak immune system response is much faster and stronger in second encounter of particular pathogen

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5
Q

Outline the principles of vaccination.

A
  • expose immune system/naïve immune cells to antigen
  • primary expansion of effector cells (clonal expansion)
  • contraction (no. effector cells decreases, put into memory)
  • second encounter = secondary expansion of effector cells (much faster and stronger)
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6
Q

How do vaccines stop infection?

A

1) Stops virus or bacteria getting into host cells - antibodies block entry, macrophage engulfs pathogen
2) Enables killing of infected cells - CD8+ killer T cells, T cells clear infected cells
3) Boosts immune responses - boosting CD4+ helper cells

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7
Q

How does clonal expansion of B cells lead to a highly specific antibody for the foreign antigen?

A

The B cell already made by our body that produces antibodies that best recognise the foreign antigen is the B cell that is selected to expand i.e. the better B cells survive (affinity maturation)

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8
Q

What is R0?

A

Basic reproduction number - no. cases one case generates on average over course of infectious period

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9
Q

What does it mean if R0 <1?

A

Infection will die out in long run

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10
Q

What does it mean if R0 >1?

A

Infection will be able to spread in a population

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11
Q

What will an effective vaccine do to R0?

A

Bring R0 to below 1

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12
Q

What is the principle behind herd immunity?

A

The more immune individuals there are, the less likely it is that a susceptible person will come into contact with someone who has the disease

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13
Q

What’s in a vaccine?

A
  • antigen (could be in one of a variety of forms)
  • adjuvant (normally alum), sometimes something proprietary
  • stabilising stuff (e.g. buffers - PBS)
  • water
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14
Q

What forms could antigen be in within a vaccine?

A
  • inactivated protein e.g. tetanus toxoid
  • recombinant protein e.g. Hep B
  • Live attenuated pathogen e.g. Polio, BCG
  • Dead pathogen e.g. Split flu vaccine
  • Carbohydrate e.g. S. pneumoniae
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15
Q

What are inactivated toxoid vaccines?

A

Chemically inactivated form of toxin

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16
Q

What is the mechanism of action of inactivated toxoid vaccines?

A

Induces antibody, antibody blocks toxin from binding the nerves
Formulin locks shape, makes it inactive

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17
Q

What are the advantages of inactivated toxoid vaccines?

A

Cheap, well characterised, safe, in use for many decades

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18
Q

What are the disadvantages of inactivated toxoid vaccines?

A

Requires good understanding of biology of infection, not all organisms encode toxins, tiny risk of failure to inactivate/impurities

19
Q

What are recombinant protein vaccines?

A

Uses recombinant protein from pathogen - gene of one organism moved to another, looks same as pathogen

20
Q

What is the mechanism of action of recombinant protein vaccines?

A

Induces classic neutralising antibodies

21
Q

What are the advantages of recombinant protein vaccines?

A

Pure, safe, because low strain variation and human only host highly protective

22
Q

What are the disadvantages of recombinant protein vaccines?

A

Relatively expensive, has not proved to be answer to all pathogens

23
Q

What are conjugate vaccines?

A

Polysaccharide coat component is coupled to an immunogenic “carrier” protein

24
Q

What is the mechanism of action of conjugate vaccines?

A

Protein enlists CD4 help to boost B cell response to polysaccharide

25
Q

What are the advantages of conjugate vaccines?

A

Improves immunogenicity, highly effective at controlling bacterial infection

26
Q

What are the disadvantages of conjugate vaccines?

A

Cost
carrier protein interference,
very strain specific,
polysaccharide alone is poorly immunogenic

27
Q

What are dead pathogen vaccines?

A

Rather than using a component of the pathogen, it can be chemically killed.

28
Q

What is the mechanism of action of dead pathogen vaccines?

A

induces antibody and T cell responses

29
Q

What are the advantages of dead pathogen vaccines?

A

Leaves antigenic components intact and in context of other antigen. Immunogenic because of the inclusion of other components.

30
Q

What are the disadvantages of dead pathogen vaccines?

A

Fixing/ killing can alter chemical structure of antigen.
Quite “dirty”.
Requires the capacity to grow the pathogen (H5N1).
Vaccine induced pathogenicity a risk.
Risk of contamination with live pathogen (Polio)

31
Q

What are live attenuated vaccines?

A

Bugs are attenuated by serial passage. Leads to loss of virulence factors.

32
Q

What is the mechanism of live attenuated vaccines?

A

Because they replicate in situ they trigger the innate response and boost the immune response.

33
Q

What do adjuvants do?

A
  • engage w/pattern recognition receptors (PRR)
  • induce ‘danger signals’ that activate dendritic cells to present antigen to T cells
  • all trigger to license the response
  • used w/specific antigen to induce more robust response
34
Q

How do adjuvants license DCs?

A
  • adjuvant stimulates DC
  • DC uptakes antigen and moves to lymph node
  • upregulates stimulatory signalling and cytokines
35
Q

What vaccines are given at 8 weeks old?

A
  • Diphtheria, tetanus, Pertussis (whooping cough), polio, Haemophilus influenzae type B (HiB) and hepatitis B (6-in-1 vaccine)
  • Pneumococcal conjugate vaccine (PCV)
  • MenB
  • Rotavirus
36
Q

What vaccines are given at 12 weeks old?

A
  • Diphtheria, tetanus, pertussis, polio, Hib and hepatitis B

- Rotavirus

37
Q

What vaccines are given at 16 weeks old?

A
  • Diphtheria, tetanus, pertussis, polio, Hib and hepatitis B
  • Pneumococcal
  • MenB
38
Q

What vaccines are given to 1 year olds?

A
  • HiB and MenC
  • Pneumococcal
  • MMR
  • MenB booster
39
Q

What may eligible paediatric age groups be given?

A

Live attenuated Influenza vaccine (each year from September)

40
Q

What vaccines are given at 3 years 4 months old?

A
  • Diphtheria, tetanus, pertussis and polio

- MMR

41
Q

What vaccines are given to girls and boys aged 12 to 13 years?

A
  • HPV (2 doses 6-24 months apart)
42
Q

What vaccines are given to 14 year olds (year 9)?

A
  • Tetanus, diphtheria and polio

- MenACWY

43
Q

What vaccines are given to people 65 years and over?

A
  • Pneumococcal
  • Influenza
  • Shingles

Principles of Medicine (POM) - Block 3 (11 decks)

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