Immunology - Vaccines Flashcards
What is the goal of vaccination?
2 aims of vaccination?
Goal is to generate long-lasting and protective immunity
Aim 1 - Eradicate disease
Aim 2 - Reduce incidence/transmission of disease
What are the 6 factors favouring global eradication of infectious disease?
- Give reasoning for each
Disease limited to human –> No reinvasion by microbe from animal or arthropod host
No long-term carrier state –> No reinvasion by microbe from human carriers
Few unrecognised clinical cases –> Surveillance possible
One or few serotypes –> Single vaccine is adequate
Stable, cheap and effective vaccine available –> Worldwide programme possible
Eradication programme is cost-effective –> Programme likely to be undertaken
Explain the concept of ‘Herd Immunity’
- What types of disease does this apply to and not apply to?
Applies to disease spread by person-to-person contact
- Risk of disease to unvaccinated person reduced if 80-95% population is vaccinated
Doesn’t apply to disease not spread by person-to-person
How do most vaccines confer protection?
What are the 3 types of vaccine and how do they work?
Through induction of antibodies
Attenuated pathogen - Virulence reduced to cause mild infection
Killed pathogen - Unable to replicate
Subunit - Molecular components of pathogen
What are the 6 features of effective vaccines?
Safe
Protective
Gives sustained protection - Lasts several years
Induces neutralising antibody
Induces protective T cells
Practical considerations
Give some differences between using attenuated live vaccines and non-living vaccines?
Non-living requires adjuvant; Ingredient added to enhance immune response to vaccines by inducing inflammation
Living induces Cell mediated response
Non-living mainly induces IgG
Living is cheaper than non-living
Are attenuated live vaccines more effective than non-living vaccines and why?
They are generally more effective
- More realistic infection at appropriate body site, inducing appropriate immune response to the pathogen
What are the methods of attenuation? (4 methods)
- Specify if for viruses, bacteria or both
Serial passage through cell culture in vitro
Serial passage in vitro (bacteria)
Adaptation to low temperature (viruses)
Genetic manipulation (both)
How are killed vaccines generated and what does this do?
Characteristics? (2 characteristics)
Inactivated (e.g. chemical treatment, heat) so they are unable to replicate
Safer, but some side effects are possible
Characteristics of sub-unit vaccines?
- What do they require? (2 things)
- Length of immunity?
Forms? (4 forms)
Safer with fewer side effects
- Requires adjuvants and multiple injections
- Shorter lived immunity
Forms include:
- Toxoid - Chemically inactivated toxin
- Recombinant protein
- Subcellular fractions
- Conjugate vaccines - Polysaccharide linked to carrier protein; Stimulates B and T cell immunity
What do recombinant vector vaccines do?
Describe structure of viral vector and internal genome?
How well does this emulate natural infection immune response?
They use a virus vector to express pathogen antigen in host cells
Viral vector made from capsule which envelops a viral vector gene containing a pathogen gene
Generates immune response similar to natural infection
How do DNA/RNA vaccines work?
How well does this emulate natural infection immune response?
They use DNA/RNA to transiently express pathogen antigen in host cells
Generates immune response similar to natural infection
What are the biological barriers to an effective vaccine? (4 barriers)
How can temperature of a region be a barrier?
Complex life-cycle of pathogen
T cell immunity needed
High mutation rate
Many types of pathogen
Vaccines can be heat-sensitive, making use difficult in tropical countries etc.
What are some non-biological barriers to a vaccine? (5 barriers)
Expense
Lack of appropriate medical infrastructure
Patient compliance
Personal/Religious objections
“Fake news”
