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POM 4: Immunity and Infection > 9: Vaccination > Flashcards

9: Vaccination Flashcards

1
Q

Vaccination

A

deliberate exposure to harmless antigenic material which stimulates immune system

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2
Q

Aim of vaccination

A

elicit T cell response inducing production of immunological memory to provide protection against disease if later encountered
- reducing morbidity and mortality of infectious disease targeted by vaccine

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3
Q

Type of immunity involved in vaccination

A

Artificial active immunity

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4
Q

Artificial active immunity is

A

artificial - haven’t encountered antigen naturally in wild form
active - generating own antibodies and own immune response against antigen

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5
Q

Acquired Immunity

A

immunity that develops during lifetime

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6
Q

Types and examples of active immunity

A

Natural - antibodies developed in response to infection
Artificial - antibodies developed in response to vaccination

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7
Q

Types and examples of passive immunity

A

Natural - antibodies received from mother, via breast milk
Artificial - antibodies received from a medicine/gamma globulin injection or infusion

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8
Q

Features of an ideal vaccine 7

A

completely safe
easy to administer
single-dose, needle-free
cheap
stable
active against all variants
life-long protection

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9
Q

Herd immunity

A

more immune individuals = less likely that a susceptible person will come into contact with someone who has the disease

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10
Q

How do vaccines work in community

A

Herd immunity
Reducing R0 number

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11
Q

R0

A

how many people an infected person is able to infect
aim of immunisation is to reduce R0 to less than 1

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12
Q

If R0<1

A

Infection will die out in long run

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13
Q

If R0>1

A

infection will be able to spread in population

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14
Q

What are vaccines composed of

A

Antigen - to stimulate immune response to target disease
Adjuvant (alum) - enhance and modulate immune response
Excipients = inactive substance serving as a vehicle or medium for vaccine;
buffer, salts, saccharides and proteins to maintain pH, osmolarity and stability of vaccine
Preservative e.g phenoxyethano
Water

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15
Q

5 types of vaccines and examples

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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16
Q

Inactivated protein vaccines

A

Example: Tetanus toxoid
Description: chemically inactivated form of toxin
Mechanism: induces antibody, antibody blocks toxin from binding in nerves

17
Q

Pros of inactivated protein vaccines

A

simple to produce
cheap
relatively safe
highly immunogenic (stimulates immune response very well)
high protective efficacy

18
Q

Cons of inactivated protein vaccines

A

Not all pathogens produce toxins
good understanding of toxin produced needed
sometimes toxin isn’t fully inactivate

19
Q

Live attenuated vaccines

A

Example: MMR, Chickenpox, LAIV (flu), OPV (polio), BCG
Description: contain mutations which hinder ability to cause disease, but can be recognised by immune system as foreign (lose virulent factors)
Mechanism: “live” so can replicate inside host, recognised as foreign - generate innate response and boost immune response

19
Q

Cons of live attenuated vaccine

A

May lose key antigens on attenuation
May develop virulent factors
Can infect immunocompromised
Can be out competed by other infections

19
Q

Pros of live attenuated vaccines

A

can replicate - only low doses needed
strong immune response (life-long immunity)
can induce strong local immune response in site where particular infection is most likely to occur (LAIV)

19
Q

Dead pathogen vaccines

A

Example: Influenza split vaccine, Hepatitis A
Description: Organism is grown and then killed either chemically (e.g with phenol or formaldehyde) or by heating
Mechanism: Antigenic components still intact so can stimulate B cell and T cell responses

20
Q

Pros of dead pathogen vaccines

A

Effective
Cheap
Simple

21
Q

Cons of dead pathogen vaccines

A

Antigen can be altered or destroyed in inactivation
Live pathogen needed to grow (risky for influenza)
live pathogen can contaminate vaccine (polio)
vaccine induced pathogenicity is a risk

22
Q

Recombinant protein vaccines

A

Example: Hep B surface antigen (HepBsAg)
Description: recombinant protein from antigen (cultured in yeast)
Mechanism: immune system will generate neutralising antibodies against the antigens

23
Q

Pros of recombinant protein vaccines

A

Pure
safe
good immune response against targeted part of pathogen
low strain variation

24
Q

Cons of recombinant protein vaccines

A

Expensive
protein structure may not be exactly the same (post-translational modifications may be absent)

25
Q

Conjugate vaccines

A

Example: S. pneumoniae, HIB
Description: Polysaccharide coat component is coupled to an immunogenic “carrier” protein
Mechanism: Protein stimulates a T cell response (via CD4) which improved B cell immune response (T cell helps affinity maturation to take place)

26
Q

Pros of conjugate vaccines

A

improves immunogenicity
highly effective against infections caused by encapsulated bacteria

26
Q

Cons of conjugate vaccines

A

Expensive
strain specific
carrier protein may interfere with immune response

27
Q

Adjuvant

A

substance used in combination with specific antigen that produces a more robust immune response than the antigen alone

28
Q

How do adjuvants stimulate a more robust immune response?

A

-Potentiate immune response by interacting with PAMPs and DAMPs (cause cell to release inflammatory mediators)
-Recognised by pattern-recognition receptors on dendritic cells
-which present antigens to T cell

29
Q

Reasons for new vaccines (5)

A

Changing (aging) Demographics
Changing Environment (Dengue/other arboviruses)
New diseases (COVID-19)
Old diseases that still cannot be fixed (HIV/TB/Malaria)
Antibiotic Resistance (MRSA, all bacteria)

30
Q

Barriers to vaccine production

A

Scientific challenges
Injection Safety
Logistics/Cold chain
Development issues - time, cost of vaccine development is high, cost of product
Public expectation of risk-free vaccines

31
Q

How does vaccine development success rate depend on antigen variability?

A

more diversity = less protective
classic immune memory will only recognise one antigenic strain
therefore vaccine antigens need to cover all the variety

32
Q

In the event of a new virus outbreak, what is used to limit spread?

A

Administration of synthetic/humanised antibodies against virus = gives short term protection against virus

33
Q

Adaptive transfer of antibodies

A

act of administering protective antibodies (either synthetically produced or humanise after being harvested from animals) to individuals to prevent infection

POM 4: Immunity and Infection (9 decks)

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