Vaccines Flashcards
What are the different types of bacterial vaccine?
Inactivated/killed
Attenuated
Subunit
Recombinant
What are the different types of viral vaccine?
Inactivated (whole virus/split)
Attenuated
Subunit
Vectored
(plasmid) DNA
mRNA
What is a recombinant vaccine?
Only express the proteins that cause an inflammatory response
give an example of a subunit bacterial vaccine
purified tetanus toxin, inactivated by treatment with formalin (tetanus toxoid) for vaccination against tetanus.
Give an example of a recombinant bacterial vaccine
purified OspA, encoded by a gene from Borrelia burgdorferi, protects dogs against Lyme disease
What are the pros and cons of infectious vaccines (live attenuated or viral vectors)
Pros:
- Replication – rapid robust immunity
- Single dose may be enough
- immunity to the backbone (vectored vaccine)
Cons:
- Potential cause mild disease
- potential for reversion to virulence
What are the pros and cons of non-infectious vaccines (inactivated vaccine)?
Pros:
- cannot cause signs of disease
- can be made rapidly
Cons:
- Less likely to stimulate both cell-mediated immunity and antibodies
- Usually requires multiple doses + adjuvant
- Duration of immunity generally short
- expensive if high level of containment required
What is the disadvantage of subunit vaccines?
often poor immune response
What are the pros and cons of mRNA and DNA vaccines?
mRNA - need to ‘maintain cold chain’
DNA
- good T-cell mediated immunity
- difficult to get strong antibody response
What is the DIVA strategy?
The differentiation of infected from vaccinated animals:
- diagnostic tests for antibodies to proteins not present in vaccine
- cannot be used with vaccines containing whole pathogen
What are the common components of vaccines?
Active ingredient - what you want to immunise against
Adjuvants - enhance immunogenecity
Stabilisers - proteins don’t denature
Preservatives - prevent growth of parasites etc
Trace components e.g., formaldehyde - not good
Give examples of different adjuvants
Aluminium salts (alum)
Oil emulsions
Squalene - a triterpene derived from shark liver oil
Liposomes
Saponins - bitter-tasting, usually toxic plant-derived secondary metabolites
Non-ionic block copolymers - surfactants made from ethylene oxide (EO) and propylene oxide (PO)
Cytokines
Lipopolysaccharide (LPS)
What is the mechanism of action of adjuvants?
- Depot formation
- Secretion of cytokines & chemokines
- Immune cell recruitment
- Antigen uptake through antigen-presenting cells (APCs)
- Maturation & activation of immune cells
- Antigen processing & presentation on MHC
- Activated APCs to traffic to draining lymph nodes
- Activate antibody-secreting B cells and CD8+ T cell responses
How is the safety of vaccines ensured?
Pre-licensing testing:
- safety
- efficacy
- effectiveness
Marketing authorisation licence:
- European medicines agency
- Veterinary medicines directorate
Post-licensing testing:
- batch-release safety tests
What are the 4 categories of adverse effects of vaccines?
Vaccine-induced effect
Vaccine-potentiated effect e.g., unknown underlying issue that is potentiated by the vaccine
Programmatic error e.g., given in wrong place, overdosing etc.
Coincident effects
What are the local and systemic adverse events you can get from vaccines?
Heat, swelling, redness at vaccine site
Lethargy, loss of appetite / fever* (pregnancy loss)
Severe allergic reaction (rare)
Feline injection site sarcoma (FISS)
What is a feline injection site sarcoma (FISS)?
Tumours (high-grade sarcomas) linked to vaccine administration
Time from vaccination to tumour development between 3 months and 4 years
Treated by excision with radiation therapy (limb amputation if in limbs - preferred site)
How can feline injection site sarcomas be avoided?
Only administer necessary vaccines
Avoid adjuvanted vaccines / use attenuated or recombinant vaccines
Follow vaccine site recommendations:
- Use distal limbs, tail, lateral abdomen
- Avoid the ‘scruff’
Use a different site each year
What factors increase the risk of adverse events due to vaccinations in dogs?
small dogs
neutered
multiple vaccines on one occasion
What is type I hypersensitivity?
IgE-mediated allergic response
IgE can precipitate degranulation of mast cells and release of histamine leading to anaphylactic shock
Usually within a few minutes
Give an example of type II hypersensitivity as a response to a vaccine
Type II - immune response to body’s own cells
e.g. Renal autoantibodies in cats:
- Vaccine viruses cultured in feline kidney cell cultures
- Contaminants may lead to auto-antibody production and cause interstitial nephritis
- Risk factors for chronic kidney disease (CKD) in cats: Annual vaccination and dental disease
What is Type III hypersensitivity and give an example of a response from a vaccine
Immune complex mediated - antigen-antibody precipitate
e.g., Rabies vaccine – cutaneous vasculitis
- Typically, a mild reaction with some hair loss
- Breed predisposition (e.g. poodle)
What is Type IV hypersensitivity
Delayed’ hypersensitivity
Mediated by T cells, which produce cytokines
Granuloma - fibrous stroma and an infiltration of macrophages, giant cells, and lymphocytes around the persistent antigen
Fill in this table describing the features of the different types of hypersensitivity
Describe the process of reporting adverse events of vaccines?
Veterinary Medicines Directorate Pharmacovigilance Team
Date reaction / lack of efficacy observed
