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
single dose, needle free
Cheap
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 eventually
What happens if R0>1?
Then the infection will be able to spread in the population
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 induce danger signals that activate DC’s to present antigen to T cells
What adjuvant is normally found in vaccines?
Alum
name some novel adjuvants in vaccines
AS03
MF59
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?
The vaccine induces antibody which blocks the toxin from binding to cells (nerves in tetanus’ case)
How do recombinant protein vaccines work?
Surface antigen gene is isolated
Inserted into another organism
Modified cell produces antigen / vaccine (protein)
Induces classic neutralizing antibodies in human
give an example of a disease which uses recombinant protein vaccines
Hep B
What are the disadvantages of a recombinant protein vaccine?
Expensive
what is a major flaw with recombinant protein vaccines?
The shape of the protein before and after the growth in a vector is different.
Hence, the antibodies produced against the vaccine protein would be ineffective against a proper infection.
This is common problem with virus’ but can easily be solved.
what is a problem associated with inactivated toxoid and recombinant protein vaccines?
Some bacteria have capsules which prevent B cell responses, so need alternative approaches against these
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, attenuance may lose key antigens
What is a dead pathogen vaccine?
Rather than using a single antigen, it’s a chemically killed pathogen using formaldehyde
what is the mechanism of dead pathogen vaccines?
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
- virus can mutate whilst growing - antigenic drift
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
give an example of a conjugate vaccine
s.pneumoniae
how do conjugate vaccines work?
- A DC engulfs the whole antigen and presents the protein part onto MHCII. A B cell takes up the polysaccharide part of the antigen and presents it onto its MHCII
- Tfh is primed by DC through interacting with the DC’s MHCII presented peptide and then goes to the matching B cell (presenting the same thing) and boosts it
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? d
Toxin Based
What type of vaccine is MMR?
Live attenuated
What type of vaccine is BCG?
Live attenuated
What type of vaccine is Influenza split vaccine
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
scientific 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
how do conjugate vaccines work?
- A DC engulfs the whole antigen and presents the protein part onto MHCII. A B cell takes up the polysaccharide part of the antigen and presents it onto its MHCII
- Tfh is primed by DC through interacting with the DC’s MHCII presented peptide and then goes to the matching B cell (presenting the same thing) and boosts it
