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SEM 4: Immunology > Scientific Basis of Vaccines > Flashcards

Scientific Basis of Vaccines Flashcards

1
Q

Which virus causes smallpox?

A

The variola virus

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2
Q

What was the difference between variola major and variola minor?

A

Someone infected with variola major has a higher chance of dying compared to variola minor.

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3
Q

What is inoculation?

A

People understood that if you inoculated a person with variola minor with an active form, then they would have some sort of protection against the infection.

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4
Q

Why did milk maids not get smallpox?

A

They were exposed to cows who have the vaccinia virus and caused cowpox so they couldn’t be vaccinated or variolated.

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5
Q

Where did the term vaccination dervive from?

A

Came from the varol cow

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6
Q

What are the 4 principles of Jenner’s experiments

A
  1. Challenge dose - provides protection from infection
  2. Concept of attenuation (live weakened vaccines)
  3. Concept that prior exposure to agent boosts protective responses
  4. Cross-species protection - antigenic similarity
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7
Q

When was smallpox eradicated?

A

Eradicated in the 1980’s - last case in Somalia in 1977.
- Vaccination programmes were used to eradicate those who were at risk of developing it. Also, stopped people from migrating out of areas where there were cases of small pox.

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8
Q

Why was the eradication of smallpox possible?

A
  1. No subclinical infection: can’t have asymptomatic people
  2. After recovery, the virus is eliminated - no carrier status
  3. No animal reservoir
  4. Effective vaccine (live vaccinia virus)
  5. Slow spread, poor transmission
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9
Q

What causes the smallpox vaccination scar?

A

A bifurcated needle that is used for inoculation causes jagged edges.

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10
Q

Define vaccine

A

Material from an organism that will actively enhance the adaptive immune response.

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11
Q

How does a vaccine work?

A
  • It increases the ability of the adaptive immune response to generate antibodies that will protect and immunise.
  • It produces an immunologically ‘primed’ state that allows for a rapid secondary immune response on exposure to antigen i.e. memory cells.
  • Long lasting and requires immunological memory - antibodies and/or T-cells.
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12
Q

Why are vaccines used?

A
  1. To protect the individual: reduce the rate/severity of the disease
  2. To protect the population: herd immunity
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13
Q

What is herd immunity?

A

Involves vaccinating as many people as possible in one population to stop the spread of infection.

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14
Q

Why does a balance between vaccine uptake rate and reservoirs of infection need to be maintained?

A

If less people take vaccines, then there a risk to the population and to individuals as there will be a higher reservoir of infection. This leads to epidemics and outbreaks.

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15
Q

What is public apprehension behind vaccines?

A
  • Strong anti-vaccine programme
  • Wakefield claimed that the MMR jab caused autism in children.
  • Notification of a case immediately.
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16
Q

What is the vaccine paradoz?

A

The more people who are vaccinated means there is a less infectious pool in the community which stops natural boosting.

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17
Q

What is natural boosting?

A

Having the immune response boosted by exposure to an infectious agent in the community.

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18
Q

Why is it important to maintain a high vaccination rate with a low infectious pool?

A

Vaccine rates need to stay high because as soon as there is a reduction, there will be an increase in the disease.

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19
Q

Why is herd immunity important?

A
  • Prevents vulnerable people in the community from developing the infection if vaccines are delivered by health professionals.
20
Q

Reasons to be vaccined against: Measles

A
  • Without: 1 in 15 children developed pneumonia, otitis media, bronchitis that is life-threatening and also encephalitis in 1 in 5000 with a 15% mortality rate.
  • With: 1 in 1000 have a slight fever/convulsions and 1 in 400,000 have meningo-encephalitis that is not life-threatening
21
Q

Reasons to be vaccined against: diphtheria

A
  • Without: causes heart and kidney damage with a 5% mortality rate
  • With: occasional swelling
22
Q

Reasons to be vaccined against: whooping coughing

A
  • Without: high mortality rate for babies and can last up to 3 months in children with frequent pneumonia, encephalopathy.
  • With: 1 in 600,000 develop encephalopathy
23
Q

What are the two types of immunity?

A
  • Active

- Passive

24
Q

What is active immunity?

A

Immunity that actively enhances the adaptive immune response e.g. cell-mediated and antibodies that are induced by natural exposure, infection and vaccination will drive the memory response. Produces a longer effect and defence.

25
Q

What is passive immunity?

A

Antibodies from another source i.e. serum from rabies disease can be given will prevent the virus from taking hold. However, there is a short effect as it doesn’t last long in the body.

26
Q

Describe the immune response to an antigen also state why it is important to be vaccinated

A
  1. Primary exposure: takes 5-7 days to get an antibody response and 2 weeks for a full response as requires the switching of IgM -> IgG
  2. Secondary exposure: full response in 2 days which is what is provided from having an early vaccine as you already have memory cells
27
Q

When are vaccines not useful?

A
  • Against infections that have an incubation period that is shorter than 2 days as antibodies have not been made such as cholera whereas the disease has already occured.
28
Q

What are the 4 general principles about vaccines?

A
  • Need to induce the correct type of response
  • Need to induce the response in the right place
  • Need to understand the duration of protection
  • Vaccination at the right age
29
Q

What places can vaccines induce a response?

A
  • Mucosal: such as the gut so sIgA stops the virus from adhering to the gut
  • Systemic: need T cells and antibodies in the bloodstream
30
Q

Why is it important to understand the duration of protection of a vaccine?

A

Some vaccines are short-term (e.g. travel vaccines) and this can be enough as little long-term memory is required. However, when long term memory is required, a booster may be neede to drive protective immunity - this can be either natural boosting or through vaccines.

31
Q

Where is it difficult to induce long-lasting immunity?

A

At mucosal surfaces

32
Q

Why is it important to vaccinate at the right age?

A

In neonates, they already have high maternal antibodies or sIgA in milk which lasts about 6 months. If vaccinated with live attenuated vaccines, the vaccine will be neutralised by maternal antibodies. So vaccines need to be given after the right age, however in 9 months, many babies in endemic areas will be infected.

33
Q

What are monotypic infections?

A

Infections where there is little/no difference in the antigenic nature of the different types of the virus e.g. measles. This means a vaccine can be used and protect all the strains.

34
Q

What are polytypic infections?

A

There is large antigenic variation and genetic diversity between the different types of virus e.g. flu, gonorrhoea. this means a vaccine is difficult to make as they change all the time.

35
Q

What are good vaccine targets?

A

Good targets are surface proteins, polysaccharides, some can also target the toxin. Post-exposure immunoprotection needs a specific antigen.

36
Q

What are the three types of vaccines?

A
  1. Live, attenuated organism
  2. Killed, whole organism
  3. Subunit vaccines
37
Q

What are live attenuated organism vaccines?

A

These are live bacterium/virus that has been attenuated in the lab by serial passage. The idea is that boosters are not needed as the organism is able to grow and give continous immune response against infection.

38
Q

What is a disadvantage of live attenuated vaccines?

A

Some have been found to become virulent again for example, polio(sabin) type 1 had mutations.

39
Q

What is a killed, whole organism vaccine?

A

A vaccine that in order to get a correct immune response, a single dose will raise the immune response however, multiple doses may be needed to raise the levels of antibodies. This will achieve good protective immunity.

40
Q

What is a subunit vaccines?

A

Where components of organisms have been identified as they give good protective immunity e.g. surface proteins, toxoids, peptides, polysaccharides, recombinant proteins etc.

41
Q

Why are polysaccharides poor antigens only?

A

They are not good at protecting children under the age of 2 as they will bind to the B cell receptor only but is not recognised as well and will produce a poor memory and immune response.

42
Q

Why is it important that polysaccharides are conjugated?

A

Conjugation with outer membrane proteins and toxoids will mean it will bind to the B cell and present a protein to a T cell which will recruit cytokines and T-helpers to encourage the B cell to make more potent antibodies at higher levels. This produces long lasting immunity and response in children e.g. MenC vaccine

43
Q

What are vaccine adjuvants?

A

Chemicals or lipid structures that enhance the immune response using the vaccine components. With an adjuvant, there is a higher antibody response that is maintained for longer.

44
Q

What are the components of an adjuvant?

A

They are a mixture of things such as aluminium salts etc. that trap the antigens in the vaccines so they are cleared less efficiently by macrophages. They also say longer in the system.

45
Q

What are the effects of vaccine adjuvants?

A
  • Trap the antigen in the vaccine so it isn’t cleared as effectively by the macrophages
  • Allow the vaccine to stay longer in the system
  • Enhances the immune response to antigens
  • Promotes the uptake and antigen presentation
  • Stimulates correct cytokine profiles.

SEM 4: Immunology (15 decks)

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