Vaccination Flashcards
What is a vaccination?
Something that stimulates the immune system, without causing serious harm or side effects
it is some form of antigen administered to the patient
What is the purpose of a vaccine?
Provoke immunological memory to protect individual against a particular disease if you later encounter it…
Reducing the morbidity and mortality of the infectious disease targeted by the vaccine.
What makes an ideal vaccine?
Completely safe Easy to administer Single dose, needle-free Cheap Active against all variants Life-long protection
What type of immunity does vaccination provide?
Artificial active immunity
Artificial - you haven’t encountered the antigen naturally in its wild form
Active - you are generating your own antibodies and own immune response against that antigen.
What is natural passive immunity?
Antibodies received from mother, through breast milk
What is passive artificial immunity?
Antibodies received from a medicine, from a gamma globulin or infusion
What is natural active immunity?
Antibodies developed in response to infection
How do vaccines work in the community?
Herd Immunity - the more immune individuals there are, the less likely it is that a susceptible person will come into contact with someone who has the disease
Reducing the R0 number
What is R0?
Amount of people an infected person can go on to infect i.e if R0=1- each infected person gives one other person the disease.
What is found in a vaccine?
Antigen
Adjuvant - normally alum, makes vaccines work better
Excipients - inactive substance serving as a medium ie
Stabilising products ie buffers, salts, proteins
Water
preservatives - phenoxyethanol
What are the different types of vaccines? AKA What are the various forms antigens can be added to a vaccine?
Inactivated protein ie tetanus toxoid Recombinant protein ie Hep B Live attenuated pathogen ie Polio/BCG Dead pathogen ie split flu Carbohydrate ie S. pneumoniae
What is an inactivated toxoid vaccine ?
Chemically inactivated form of toxin
Tetanus toxoid
What is the mechanism for inactivated toxoid vaccines?
Induces antibody and the antibody blocks the toxin from binding the nerves
What are the advantages and disadvantages of an inactivated toxoid vaccine?
Adv - cheap, well characterised, safe, in use for decades
Dis - Not all organisms use toxins, requires good biological understanding
What are recombinant protein vaccines?
Recombinant protein from pathogen - make a protein similar to one that the pathogen produces
What is the mechanism for a recombinant protein vaccine?
Induces classical neutralising antibodies
What are the advantages and disadvantages of recombinant protein vaccine?
Pure, safe
relatively expensive, has not been useful for all pathogens
Why doesn’t the inactivated / recombinant approach for vaccines work well with bacteria?
Only works well for protein options
but bacteria don’t often have protein on their surfaces
they have a polysaccharide capsule which is not good at inducing a B cell response
What is a conjugate vaccine?
A polysaccharide coat is coupled to an immunogenic carrier protein
S. pneumoniae, HIB
What is the mechanism for a conjugate vaccine?
Protein enlists CD4 help to boost B cell response to the polysaccharide
T cell recognises sugar and B cell recognises protein and interact to license a better B-cell response
What are the advantages and disadvantages of a conjugate vaccine?
Adv - Improves immunogenicity, effective against bacteria
Dis- Cost, strain specific, carrier protein interference
What is a dead pathogen vaccine?
Chemically killed pathogen
Influenza split vaccine
What is the mechanism for a dead pathogen vaccine?
Induces antibody and T cell responses
What are the advantages and disadvantages of a dead pathogen vaccine?
adv- leaves antigen components intact and in context of other antigen
Immunogenic because of the inclusion of other components
dis- killing can alter structure of antigen
Dirty
pathogen must be grown first
vaccine induced pathogenicity
What is a live attenuated vaccine?
MMR, Chickenpox, LAIV (influenza), OPV (polio), BCG
Pathogens are attenuated by mutations which hinder their ability to cause disease but still can be recognised by the immune system as foreign (lose their virulent factors)
What is the mechanism for a live attenuated vaccine?
‘Live’ so can replicate inside the host and are recognised as foreign - so they generate an innate response and boost the immune response.
What are the advantages and disadvantages of a live attenuated vaccine?
adv - strong immune response
dis - can revert to virulence, affect the immunocompromised, attenuation can lose antigens
Why doesn’t making a recombinant protein work for RSV F?
Has a protein spike that changes shape on its surface so recombinant RSV F makes a structure similar to post fusion RSV F and not pre fusion RSV F
What is an adjuvant and what does it do?
Substances used in combination with specific antigen that produced a more robust immune response than the antigen alone
Induce danger signals DAMPs and PAMPs that activate dendritic cells through inflammatory mediators to present antigen to T cells
Why do we need new vaccines?
Changing demographics (ageing) Environment change New diseases Old unfixed diseases Antibiotic resistance - variants
What are some barriers to making new vaccines?
Scientific challenge Cost of product Logistics Development time/cost Public expectation or risk free vaccines
How does vaccine development success rate depend on antigen variability?
The more diversity, the less protective
Classic immune memory will only recognise one antigenic strain
Therefore vaccine antigens need to cover all the variety
