Vaccination Flashcards
What is a vaccine?
A substance used to stimulate the production of antibodies and provide immunity against one or more diseases
What is the aim of immunisation?
To provoke immunological memory and protect individuals against a particular diseases if encountered
What are some characteristics of the ideal vaccine?
Safe Easy to administer Cheap Can be stored for longer periods of time Active against all variants Life-Long protection
What three things can vaccines work to do?
- Prevent entry - vaccine stimulates production of antibodies which bind to virus and stop it harming cells
- Boosting immune response - the antigens in the vaccine stimulate CD4 Helper T cells
- Killing Infected cells - CD8 killer cells detect the foreign antigens
What are the characteristics of immune memory?
The memory cells can multiply much faster and produce a stronger immune response by generating antibodies which have a higher affinity for antigens
What is R0?
The basic reproduction number - the number of cases one case generates on average over the course of their infectious period
What happens if R0 <1?
The infection will die out ebventually
What happens if R0>1?
Then the infection will be able to spread in the population
What is the effective number and why is it more useful?
It is similar to R0 but does not assume that everyone is susceptible, and therefore takes into account that people may be immune - helpful as then the true severity can be determined
What is herd immunity?
Those people who are immunised against the virus can help protect those who are not as the virus will be less transmissible amongst those protected
What are the four components of a vaccine?
antigen
adjuvant
stabilising factors eg buffers
water
What is an adjuvant?
Substances used alongside the antigen to illicit a more robust immune response than if the antigen was just used alone
How do adjuvants work?
They engage with pattern recognition proteins which induce danger signals that activate DC’s to present antigen to T cells
What adjuvant is normally found in vaccines?
Alum
Mechanism of adjuvant action?
- Adjuvant stimulates DC
- DC take up antigen and moves to secondary lymphoid tissue
- Upregulation of co-stimulatory signalling and cytokines
What is an Inactivated Toxoid Vaccine?
A chemically inactivated form of toxin
Benefits of inactivated toxoid vaccines?
Cheap, Safe
Mechanism of Inactivated Toxoid Vaccines?
- Toxin binds to cell surface receptor
- Toxin/Receptor complex enters cell via endocytosis
- Dissociation of toxin releases active chain which causes the cell to be poisoned
- The neutralizing antibody are then produced, and blocks further binding of toxin to cell surface receptor
How do recombinant protein vaccines work?
Surface antigen gene is isolated
Inserted into another organism
Modified cell produces antigen / vaccine
Induces classic neutralizing antibodies
What are the disadvantages of a recombinant protein vaccine?
Expensive
What is a live attenuated pathogen vaccine?
Vaccine where the pathogen has been weakened, but is still able to replicate so it can trigger an immune response, which is almost identical to what happens in a natural infection
What is an example of an live attenuated pathogen vaccine?
MMR, BCG
What are the advantages and disadvantages of a live attenuated pathogen?
Advantages: Strong immune response is generated
Disadvantages: Since it is a pathogen, it may infect the immunocompromised, can revert to virulence
What is a dead pathogen vaccine?
Where the pathogen has been chemically killed by formalin, which induces antibody and T cell responses
what is an example of a dead pathogen vaccine?
influenza
What are some disadvantages of a dead pathogen virus?
killing the pathogen can sometimes alter the antigen
requires the capacity to grow the pathogen
what is a conjugate vaccine?
Where the polysaccharide coat component is coupled to an immunogenic “carrier” protein which enlists CD4 help to boost B cell response to the polysaccharide, as B cell react strongly to the polysaccharides on some bacteria
The polysaccharide is considered a highly immunogenic part
Conjugate vaccines involve T and B cells true or false?
False - only B cells
Why do we need new vaccines?
- changing demographics
- changing environments
- new diseases emerging
- increasing resistance
- old diseases we cant fix
What type of vaccine is Diptheria?
Toxin Based
What type of vaccine is MMR?
Live attenuated
What type of vaccine is BCG?
Live attenuated
What type of vaccine is Influenza A
Dead pathogen virus
What type of vaccine is polio?
Live attenuated
What are some barriers to future vaccine development?
Time, cost and expertise required to develop vaccines
Systematic challenges
Vaccine safety
Public expectation of free vaccination
What makes it harder to generate vaccines?
Classic immune memory will only recognise one strain
Therefore vaccine antigens need to cover all the variety
What are the phases of a clinical trial?
Pre-clinical
Phase 1 - safety in humans
Phase 2 - mixture of safety and efficacy studies
Phase 3 - shown to be safe and effective
FDA review (MHRA in UK) - licensing
Phase 4 - licensed and approved → then goes into large groups of people + more monitoring
What needs to be considered for the scheduling of the vaccine?
Aim
Need
Scheduling with other vaccines
Availability
Cost
Population accessibility
Cultural attitudes and practices
Facilities available for delivery
Give an example of a high variable virus?
HIV
