Microbiology 8 - Defence and Vaccination Against Bacteria Flashcards

1
Q

What is direct protection in vaccine use?

A

This is preventing a healthy person being infected by vaccinating the individual.

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2
Q

What is indirect protection by use of vaccines?

A

Herd immunity - everyone is vaccinated in a population to isolate the disease, so that unvaccinated people are much less likely to come into contact with an infected individual.

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3
Q

What occurs in phase 1 trials of vaccines?

A

The vaccine is tested on a small number of adults to assess safety.

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4
Q

What happens in phase 2 trials of vaccines?

A

The immune response is assessed as well as safety - the people involved are those who are in target groups for the vaccine.

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5
Q

What happens in phase 3 trials of vaccines?

A

Protection studies are performed (often placebo controlled double blind trials). There must be statistically significant data generated, and disease surveillance must be accurate - clear endpoint.

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6
Q

What is efficacy?

A

The measure of a vaccines ability to offer protection.

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7
Q

What are effectiveness studies sometimes refered to as?

A

Phase 4 studies - they are less scientific, performed to convince users of the benefits.

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8
Q

How and when is vaccine efficacy calculated?

A

Calculated in phase III trials.

Vaccine efficacy = 1-(attack rate in vaccinated group/attack rate in unvaccinated group)

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9
Q

How is the vaccine coverage needed to achieve herd effect calculated?

A

(1-1/Ro (basic reproduction number))/effectiveness

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10
Q

How and when is herd effect determined?

A

Determined post vaccine introduction

Heard effect=1-(attack rate unvaccinated post-introduction)/attack rate unvaccinated pre-introduction

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11
Q

List the three components of vaccine formulations

A

Antigen, adjuvant and excipients

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12
Q

How do antigen vaccines work?

A

They stimulate the immune response to the target disease.

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13
Q

How do adjuvants in vaccines work?

A

They enhance and modulate the immune response. They may be delivery systems, which release antigen slowly (mineral salts/liposomes), or they may be immune potentiators (toxins, lipids, peptidoglycan, cytokines or hormones).

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14
Q

How do excipients in vaccines work?

A

They involve buffers, salts and proteins which maintain the pH, osmolarity and stability of a vaccine - may contain a preservative to prevent contamination if the same vial is used multiple times.

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15
Q

What is vaccinated against in the UK childhood immunisation programme?

A
  • Rotavirus
  • Meningitis B (hamophilus influenzae)
  • Tetanus and diptheria toxoids
  • Whooping cough
  • Polio
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16
Q

What is the adjuvant present in paediatric combination vaccines?

A

Aluminium phosphate

17
Q

Compare the use of aP and wP vaccines in whooping cough.

A
  • aP is acellular, wP is whole cell
  • wP is more effective, as patients that have the aP vaccine dont have a T lymphocyte response, so they dont clear the infection very fast and infected people can still transmit the pertussis.
18
Q

How do conjugate vaccines work?

A

The antigen used is large and linear, so that it is not easily degraded. It contains a highly repetitive determinant. The immune response created mainly uses IgM, so has a poor memory effect and low avidity antibodies are produced. Therefore, repeated doses are required.

19
Q

What do conjugate vaccines usually contain?

A

A weak antigen, such as a polysaccharide, is attached to a strong protein carrier to elicit a stronger immune response.

20
Q

When are conjugate vaccines useful?

A

When humoral immunity is required. They reduce carriage and give a long lived, boostable immunity.

21
Q

List some licensed conjugate vaccines.

A
  • Pneumococcal conjugates (7/10/13 valent)
  • Men C conjugates + men ACWY
  • Geoup B strep (in the future)
22
Q

What is serotype replacement?

A

Use of a vaccine with 10 out of 100 serotypes resukts in highly virulant serotypes increasing, compromising the vaccine use.

23
Q

List some other bacterial vaccines.

A
  • BCG is the TB vaccine
  • Vivotif or Vipolysaccharide are used in typhoid vaccines
  • Cholera vaccines (killed whole cell)
24
Q

What do immunostimulatory adjuvant componants usually contain?

A

PAMPs, which are recognised by receptors on the innate immune system to cause cells to produce cytokines and influence the other cells in the immune system.

25
Q

What is the name of the pattern recognition receptors in immune cells?

A

Toll like receptors (TCRs) which are present on dendritic cells and macrophages.