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POM IMMUNOLOGY > Vaccination > Flashcards

Vaccination Flashcards

1
Q

What is a vaccine?

A

A substance 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 and protect individuals against a particular diseases if encountered

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3
Q

What are some characteristics of the ideal vaccine?

A

Safe
Easy to administer
Cheap
Single-dose, needle-free
Stable/ Can be stored for longer periods of time
Active against all variants
Life-Long protection

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4
Q

What are the only types of viruses that can be completely eradicated?

A

human viruses (viruses that are only spread between humans)

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5
Q

What three things can vaccines work to do?

A
  1. Prevent entry - vaccine stimulates production of antibodies which bind to virus and stop it harming cells
    - Macrophage: engulfs pathogen
  2. Boosting immune response - the antigens in the vaccine stimulate CD4 Helper T cells
    B cell: Makes Ig
    CD4 t cells: helps
  3. Killing Infected cells - CD8 killer cells detect the foreign antigens
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6
Q

What are the characteristics of immune memory?

A

The memory cells can multiply much faster and produce a stronger immune response by generating antibodies which have a higher affinity for antigens

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7
Q

What is R0?

A

The basic reproduction number - the number of cases one case generates on average over the course of their infectious period

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8
Q

What happens if R0 <1?

A

The infection will die out eventually

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9
Q

What happens if R0>1?

A

Then the infection will be able to spread in the population

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10
Q

What is the effective number (Rt) and why is it more useful?

A

It is similar to R0 but does not assume that everyone is susceptible, and therefore takes into account that people may be immune - helpful as then the true severity can be determined

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11
Q

What is herd immunity?

A

Those people who are immunised against the virus can help protect those who are not as the virus will be less transmissible amongst those protected

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12
Q

What needs to happen in terms of vaccines if R0 is high?

A

more people need to be immunised for herd immunity to work

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13
Q

What are the four components of a vaccine?

A

Active ingredient/ antigen
adjuvant (normally alum)
preservatives stabilising factors eg buffers
water (main ingredient)

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14
Q

What are active ingredients?

A

A very small amount of a harmless form of the bacteria or virus you are immunising against

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15
Q

What is an adjuvant?

A

Substances used in combination with the specific antigen to elicit a more robust immune response than if the antigen was just used alone
- has no significant risk to health as it’s very small quantities used

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16
Q

How do adjuvants work?

A

They engage with pattern recognition proteins which induce danger signals that activate DC’s to present antigen to T cells

Adjuvant stimulates the DC
DC uptakes antigen and moves to Lymph node
Upregulates stimulatory signalling and cytokines

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17
Q

What adjuvant is normally found in vaccines?

A

Alum

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18
Q

What are 2 new platforms for adjuvants?

A

AS03 – GSK adjuvant in a number of different vaccines e.g.
Shingrix (chicken pox) Mosquirix (malaria)
New experimental TB New experimental COVID

MF59 – In Seqirus influenza vaccine

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19
Q

Mechanism of adjuvant action?

A
  1. Adjuvant stimulates DC
  2. DC take up antigen and moves to secondary lymphoid tissue
  3. Upregulation of co-stimulatory signalling and cytokines
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20
Q

What forms of antigen can be found in a vaccine? (CRILD)

A

Inactivate protein e.g., tetanus toxoid
Recombinant protein
Live attenuated pathogen
Dead pathogen
Carbohydrate

21
Q

What is an Inactivated Toxoid Vaccine?

A

A chemically inactivated form of toxin

22
Q

Benefits of inactivated toxoid vaccines?

A

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

23
Q

Mechanism of Inactivated Toxoid Vaccines?

A

Induces antibody
Antibody blocks the toxin from binding the nerves

24
Q

What are disadvantages of toxoid vaccines?

A

Requires good understanding of biology of infection, not all organisms encode toxins

25
Q

What is an example of recombinant protein vaccines?

A

Hep B surface antigen (HbSAg)

26
Q

How do recombinant protein vaccines work?

A

It is a recombinant protein from pathogen
It induces classic neutralising antibodies

27
Q

What are the disadvantages of a recombinant protein vaccine?

A

Expensive, not very immunogenic, has not proved to be answer to all pathogens

28
Q

Why are recombinant protein vaccines not effective towards all pathogens?

A

Protein structure is critical

29
Q

What is a live attenuated pathogen vaccine?

A

Vaccine where the pathogen has been weakened, but is still able to replicate so it can trigger an immune response, which is almost identical to what happens in a natural infection

30
Q

What is an example of an live attenuated pathogen vaccine?

A

LAIV, BCG

31
Q

What is a live attenuated vaccine?

A

Pathogens are attenuated by serial passage. This leads to a loss of virulence factors.

32
Q

What are the advantages and disadvantages of a live attenuated pathogen?

A

Advantages: Strong immune response is generated, can induce a local immune response in the site where infection might occur

Disadvantages: Since it is a pathogen, it may infect the immunocompromised, can revert to virulence, attenuation may lose key antigens, can be outcompeted by other infections

33
Q

What is the mechanism for live attenuated vaccines?

A

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

34
Q

What is a dead pathogen vaccine?

A

Where the pathogen has been chemically killed by formalin, which induces antibody and T cell responses

35
Q

what is an example of a dead pathogen vaccine?

A

influenza

36
Q

What are some disadvantages of a dead pathogen virus?

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)
37
Q

what is a conjugate vaccine?

A

Where the polysaccharide coat component is coupled to an immunogenic “carrier” protein
Which enlists CD4 help to boost B cell response to the polysaccharide, as B cell react strongly to the polysaccharides on some bacteria

The polysaccharide is considered a highly immunogenic part

38
Q

What are advantages and disadvantages of conjugate vaccines?

A

Advantages:
Improves immunogenicity
highly effective at controlling bacterial infection

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

39
Q

How do conjugate vaccines work?

A

extra…
- dendritic cell chops up protein part

  • B cell recognises bacterial sugar
40
Q

Conjugate vaccines involve T and B cells true or false?

A

False - only B cells

41
Q

Why do we need new vaccines?

A
  • changing demographics
  • changing environments
  • new diseases emerging
  • increasing (antibiotic) resistance
  • old diseases we can’t fix
42
Q

What are some barriers to future vaccine development?

A

Scientific challenges
Injection safety
Logistics/ Cold chain
Development issues (15 yrs now)
Cost of production
Public expectation of risk-free vaccines

43
Q

What are traditional vaccine effective at?

A

Eliciting humoral responses
And are protective against invariant agents
The more diversity, the less protective

44
Q

What makes it harder to generate vaccines?

A

Classic immune memory will only recognise one strain

Therefore vaccine antigens need to cover all the variety

45
Q

What are the types of vaccines made for COVID-19?

A

protein
inactivated
VLP
love recombinant viral vector
live attenuated
DNA
saRNA
mRNA

46
Q

What are the phases of a clinical trial?

A

Pre-clinical
(the the drug is approved for testing in humans)

Phase 1 - safety in humans (20-80 participants)

Phase 2 - mixture of safety and efficacy studies (100-300)

Phase 3 - shown to be safe and effective (1000-3000)
(then the drug is submitted for FDA approval)

FDA review (MHRA in UK) - licensing (The drug has been approved)

Phase 4 - licensed and approved → then goes into large groups of people + more monitoring (1000+)

47
Q

How are new vaccines introduced into the UK schedule?

A
  • Recommendations for vaccine policy
    Joint Committee on Vaccination and Immunisation (JCVI)
  • Vaccine policy decisions
    Department of Health (DH)
  • Licensing of vaccine
    Medicines and Healthcare products Regulatory Agency (MHRA)
  • Purchase of vaccine
    Department of Health from pharmaceutical companies
  • Control of vaccine (including batch release)
    National Institute for Biological Standards and Control (NIBSC)
  • Post licensure assessment and changes
    PHE/ JCVI (Epidemiology, assessment, trials)
48
Q

What needs to be considered for the scheduling of the vaccine?

A

Aim

Need

Scheduling with other vaccines

Availability

Cost

Population accessibility

Cultural attitudes and practices

Facilities available for delivery

49
Q

Give an example of a high variable virus?

A

HIV

POM IMMUNOLOGY (13 decks)

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