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MICRO - Abbie > 6. Bacterial and viral vaccines > Flashcards

6. Bacterial and viral vaccines Flashcards

1
Q

What is R0?

A

The number of people that one sick person will infect on average is called R0. If the R0 is reduced to < 1, transmission of disease is halted. (NOTE: Measles has a high R0 (18))

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2
Q

What is herd immunity?

A

form of immunity that occurs when vaccination of a significant proportion of the population provides a measure of protection for individuals that are not immune.

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3
Q

What is the herd immunity threshold?

A

Herd Immunity Threshold = 1 - 1/R0. This is the percentage of fully immune individuals required to stop the spread of disease.

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4
Q

With regards to immunology, what do vaccinations mainly target?

A

Lymphocytes and the production of antibodies

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5
Q

What happens during an immune response to vaccination?

A
  1. Antigen is delivered by the vaccine, which is then taken up by antigen presenting cell.
  2. APC presents antigen to naive T helper cell which becomes activated.
  3. This in turn results in activation of B cells.
  4. B cells get activated and mature into plasma cells.
  5. The plasma cells will produce antibodies specific for vaccine antigen.
  6. Antibodies then bind to antigen leading to: neutralisation of infectivity and antibody-dependent cellular cytotoxicity.
  7. Main goal is to produce memory cells to the vaccine antigen. (If attenuated virus vaccine is used, T cell response is very important in destroying infected cells).
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6
Q

What are the three main types of memory cells?

A

Memory B cells, memory killer T cells, and memory T helper cells

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7
Q

What are protective antigens?

A

These are microbial components that give rise to a protective immune response to future infection. These are often used in the development of vaccines. Some may require an adjuvant to make it more immunogenic.

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8
Q

What are the different types of vaccines?

A

Inactivated, live attenuated, toxoid, subunit, conjugate, heterotypic, monovalent and multivalent

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9
Q

How do inactivated vaccines work?

A

Whole microorganism is destroyed by heat, chemicals, radiation or antibiotics. It has no risk of causing infection in the host. However, it may not produce a very strong or long-lasting immune response.

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10
Q

Examples of inactivated vaccines?

A

Influenza, polio and cholera

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11
Q

How do live attenuated vaccines work?

A

Live organisms are modified to be less virulent. There is a risk of virulence. It is avoided in pregnant women and immunocompromised patients.

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12
Q

What are examples of live attenuated vaccines?

A

MMR, yellow fever

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13
Q

How do toxoid vaccines work?

A

Inactivated toxin components

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14
Q

What are examples of toxoid vaccines?

A

Diphtheria and tetanus

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15
Q

How do subunit vaccines work?

A

Protein components of the microorganism or synthetic virus-like particles are used. They lack viral genetic material and are unable to replicate.

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16
Q

What are examples of subunit vaccines?

A

Hepatitis B, HPV.

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17
Q

How do conjugate vaccines work?

A

Poorly immunogenic antigens are paired with a protein that is highly immunogenic (adjuvant)

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18
Q

What is an example of a conjugate vaccine?

A

Haemophilus influenzae type B

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19
Q

How do heterotypic vaccines work?

A

Using pathogens that infect other animals but do NOT cause disease in humans or causes mild disease.

20
Q

What is an example of a heterotypic vaccine?

A

BCG

21
Q

How do monovalent vaccines work?

A

Targeting one strain

22
Q

How do multivalent vaccines work?

A

Targets several strains

23
Q

What are components of vaccines?

A

Stabilisers (to keep vaccine chemically stable for transport from the site of production to the site of use); aluminium hydroxide (commonly used adjuvant); preservatives (especially for multi-use vaccines where you don’t want the vials to be contaminated); antibiotics (prevent contamination); trace components (e.g. formaldehyde left behind from the vaccine manufacture process).

24
Q

What are determinants of antibody response to a vaccine?

A

Vaccine type (live attenuated>inactivated etc.), antigen nature, vaccination schedule

25
Q

What are contraindications to all vaccines?

A

A confirmed anaphylactic reaction to a previous dose of the vaccine or to a component of the vaccine.

26
Q

What are precautions to take with all vaccines?

A

Postpone if individual acutely unwell on day of vaccination, pregnancy.

27
Q

What are precautions to take with DTP?

A

If evidence of evolving neurological abnormality or current neurological deterioration, including poorly controlled epilepsy, immunisation should be deferred until condition stabilised.

28
Q

What are contraindications to influenza?

A

A confirmed anaphylactic reaction to a previous dose of the vaccine or to a component of the vaccine. Individuals with confirmed anaphylactic hypersensitivity to egg products.

29
Q

What are precautions to influenza?

A

Where possible, thiomersal free influenza vaccines recommended for pregnant women and infants.

30
Q

What are contraindications to live vaccines?

A

A confirmed anaphylactic reaction to a previous dose of the vaccine or to a component of the vaccine. Immunocompromising treatment or condition. Pregnancy.

31
Q

What are precautions for live vaccines?

A

If ITP following previous MMR vaccine, perform antibody test. If confirmed anaphylactic reaction to egg, seek further advice with view to immunisation under controlled conditions.

32
Q

DTP has established causality with what serious reaction?

A

Anaphylaxis

33
Q

What vaccine is probably causal of encephalopathy and shock?

A

DTP

34
Q

OPV/IPV has established causality with that serious reaction?

A

Poliomyelitis (OPV)

35
Q

What vaccine is probably causal of Guillain Barre Syndrome?

A

OPV/IPV

36
Q

Measles has established causality with that serious reaction?

A

Thrombocytopenia

37
Q

What vaccine is probably causal of anaphylaxis?

A

Measles

38
Q

Rubella has established causality of what serious reaction?

A

Acute arthritis

39
Q

What vaccine is probably cause of GBS and brachial neuritis?

A

T/DT/Td

40
Q

T/DT/Td has established causality of what serious reaction?

A

Anaphylaxis

41
Q

Hepatitis B has established causality of what serious reaction?

A

Anaphylaxis

42
Q

To eliminate a disease what should the effective R0 be?

A

Needs to be <1

43
Q

What are prerequisites for successful disease eradication?

A

Example: smallpox. No animal reservoir. Antigenically stable pathogen with only one/few strains. No latent reservoir of infection and no integration of pathogen genetic material into the host genome. Vaccine must induce a lasting and immune response. High coverage required for very contagious pathogens (e.g. measles).

44
Q

How does measles present?

A

Fever, rash (appearing roughly 4 days after the fever), conjunctivitis, coryzal symptoms

45
Q

When are patients with measles infectious?

A

Patients with measles are usually infectious from 4 days before the rash to about 4 days after the rash

46
Q

How successful is a single and second dose in measles?

A

A single dose is successful in inducing immunity in about 90% of people. A second dose increases this percentage to 99%

47
Q

Do we still see measles cases? Why? In who? And when did we see a rise?

A

Measles has been declared as eliminated in the UK since 2016, however, this does NOT mean that we stop seeing cases of measles. There was a brief rise in measles cases in around 2005 due to a reduction in uptake of the vaccination following Wakefield’s paper. Currently there are some 15-20 years olds who are unvaccinated due to the reduction in uptake in the early 2000s. There has been a very recent rise in measles cases in 2016-17.

MICRO - Abbie (19 decks)

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