Immunisation ✅ Flashcards
What can immunisation be broadly divided into?
- Active
- Passive
What does active immunisation involve?
Administration of a foreign antigen(s) into an individual to stimulate an immune response
What does passive immunisation involve?
Administrating protective immune components themselves, usually specific antibodies
What are the types of active immunisations?
- Live, attenuated vaccines
- Inactivated vaccines
- Subunit vaccines
Give 3 examples of live attenuated vaccines?
- MMR
- Rotavirus
- BCG
What do live attenuated vaccines contain?
Modified organisms which replicate but do not cause disease
How do live attenuated vaccines work?
They induce a protective immune response
What are the advantages of live attenuated vaccines?
- Optimal immune response
- Low amounts of antigen can be given
- May be administered via same route as natural infection
Why do live attenuated vaccines lead to an optimal immune response?
Because the immune system is exposed to antigens in the normal configuration
Why can low amounts of antigen be given in live attenuated vaccines?
Because replication occurs
What is the advantage of administering live attenuated vaccines by the same route as natural infection occurs?
It induces local mucosal as well as systemic immunity
Who can not have live attenuated vaccines?
Immunocompromised individuals
Why can immunocompromised individuals not have live attenuated vaccines?
Even modified organisms may cause significant disease
Give 2 examples of inactivated vaccines
- Inactivated polio
- Influenza
How are inactivated vaccines produced from whole organisms?
Chemical or heat treatment
What is the difference between the antigens provided in inactivated vaccines compared to live attenuated vaccines?
In inactivated vaccines, all antigens are usually present, but usually not in their natural confirmation
Why is more antigen required in inactivated vaccines compared to live attenuated vaccines?
No replications occur
How are inactivated vaccines administered?
Generally intramuscularly
What is the limitation of giving inactivated vaccines in immunocompromised individuals?
May induce a reduced immune response
Give 4 examples of subunit vaccines
- Diptheria
- Pneumococcal
- HPV
- HBV
What do subunit vaccines contain?
Only the critical antigen(s) of the organisms needed to induce an immune response
What is usually required with subunit vaccines?
Adjuvants to induce a sufficient immune response
What does passive immunisation involve?
Administering pathogen-specific antibody after known exposure
When is passive immunisation used?
- In individuals who are unable to mount their own immune response
- When rapid protection is desired
What is the limitation of passive immunisation?
No immune memory is generated, so the individual soon becomes susceptible again
Give an example of a pathogen that passive immunisation may be used against?
Varicella zoster (VSV)
How is passive immunisation against VZV achieved?
By administering varicella zoster immunoglobulin (VZIG)
When is passive immunisation against VZV used?
In non-immune, immunocompromised individuals after significant exposure to VZV
How long does protection from VZV from passive immunisation last?
3-4 weeks
By how much does passive immunisation against VZV reduce the risk of chickenpox?
50%
How is VZIG produced?
It is a pooled blood product
What is the result of VZIG being a pooled blood product?
Risks of hypersensitivity reactions and transmission of infective agents
How have vaccines be historically produced?
Laboratory modification and attenuation of the pathogen
What is the aim of clinical trails in vaccines?
- Demonstrate the modified pathogen doesn’t cause disease
- Demonstrate a protective immune response occurs
What can help identify which components of a pathogen may be protective?
Studies of the immune response in the blood from individuals after infection
What is a new approach to produce vaccines?
Reverse vaccinology
What has allowed the development of reverse vaccinology techniques?
The ability to perform sequencing of whole genomes
How is reverse vaccinology performed?
Pathogen genome sequences are used to predict immunogenic components, and these sequences are used to produce recombinant proteins in vitro as a vaccine
What was the first vaccine created from reverse vaccinology techniques?
Capsular group B meningococcal vaccine
What are conjugate vaccines?
Vaccines where a polysaccharide antigen is linked to a carrier protein
Why are conjugate vaccines required?
Polysaccharide antigens alone to do not recruit T cell help
What is the result of polysaccharide antigens alone not recruiting T-cell help?
- Do not stimulate immune response in children under 2 years of age
- Do not lead to immunological memory and cannot be boosted
How do conjugate vaccines work?
The immune system is tricked into processing the polysaccharide like a protein, engaging help from T-cells
What is the purpose of adjuvants and multiple dosage schedules in vaccines?
Stimulate a protective and long-lasting immune response
What is the purpose of adjuvants in vaccines?
- Skew the immune response in one direction or the other (e.g. increased humeral or cell-mediated immunity)
- Increase the amplitude of the response
What is required for persistent protection from most current vaccines?
Multiple doses
What is the role of the initial dose of vaccine?
- Prime the immune system
- Provide short term protection for the most vulnerable
What is the purpose of booster doses of vaccines?
Generate greater responses that last longer
How do neonates achieve protection against infections in the first few weeks of life?
Transplancental transfer of IgG in the third trimester
How is herd immunity obtained?
High levels of vaccine coverage
How does high levels of vaccine coverage lead to herd immunity?
Transmission is reduced sufficiently that even un-immunised individuals will be protected
What does the level of vaccine coverage required to produce herd immunity depend on?
How infectious a pathogen is
What happens to herd immunity if vaccination coverage levels drop?
Disease recurs
What to immunisation programmes change to take into account?
- Epidemiological changes
- Disease reduction in a population
- Availability of new cost-effective vaccines
How are adverse effects of vaccines reported?
Yellow card scheme
What are the common adverse effects of vaccines?
- Pain
- Erythema
- Swelling
- Fever
- Malaise
- Myalgia
- Anorexia
Why is post-licensure surveillance vital with vaccination?
To ensure that rare adverse events (which would not be apparent during clinical trials) are identified
What is done when a rare adverse event of a vaccine is identified?
A risk/benefit analysis determines if a vaccine should continue to be used
