Vaccines Flashcards
What is a vaccine?
Substance used to stimulate immunity to particular infectious disease or pathogen, typically prepared from inactivated or weakened form of causative agent or from its constituents or products
Describe the perfect vaccine
Immune response that is:
- strong
- lifelong
- appropriate immune response
- in the right place
Safe
Cheap
Easy to administer
What are the types of bacterial vaccines?
Inactivated / killed
Attenuated
Subunit (e.g. purified tetanus toxin, inactivated by treatment with formalin (tetanus toxoid) for vaccination against tetanus)
Recombinant (e.g. purified OspA, encoded by gene from Borrelia burgdorferi, protects dogs against Lyme disease)
What are the types of viral vaccines?
Inactivated (whole virus / split)
Attenuated
Subunit
Vectored
(Plasmid) DNA
mRNA
What are the pros and cons of infectious vaccines (e.g. live attenuated)?
Replication – rapid robust immunity
Single dose may be enough
Potential cause mild disease
What are the pros and cons of non-infectious vaccines (e.g. inactivated)?
Less likely to stimulate both cell-mediated immunity & antibodies
Cannot cause signs of disease
Usually requires multiple doses + adjuvant
Duration of immunity generally short
What are the common components of vaccines?
What are adjuvants?
They enhance immunogenicity (Provoke immune response)
Give some examples of adjuvants
Chemicals, microbial components, or mammalian proteins
- Aluminium salts (alum)
- Oil emulsions
- Squalene - 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) & propylene oxide (PO)
- Cytokines
- Lipopolysaccharide (LPS)
What are the different causes of adverse events?
Vaccine-induced effect (something wrong with vaccine)
Vaccine-potentiated effect (underlying issue in body)
Programmatic error (e.g. overdosing)
Coincident effects
What are the types of adverse events?
Local or systemic
- Heat, swelling, redness at vaccine site
- Lethargy, loss of appetite / fever* (pregnancy loss)
- Severe allergic reaction (rare)
What is feline injection site sarcoma (FISS)?
Tumours (high-grade sarcomas) linked to vaccine administration
Time from vaccination to tumour development 3m to 4y
Radical excision with radiation therapy recommended for tumours in skin over thorax or abdomen; limb amputation for tumours at injection sites on limb
High recurrence rates
Role of adjuvants, genetics
How can FISS 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
- Either record site on vaccination card or adopt policy practice for each year
Describe a type 1 hypersensitivity caused by a vaccine
IgE-mediated allergic response
IgE can precipitate degranulation of mast cells & release of histamine leading to anaphylactic shock
Usually within a few minutes
e.g. some vaccines have gelatin in it & if allergic can have reaction to those vaccines
Fill in the table with hypersensitivity reactions to vaccines
What are the key advantages & disadvantages of inactivated/killed vaccines?
They can be made rapidly
Expensive if high level of containment is required
Have short duration of immunity
What is a major drawback of subunit vaccines?
They often produce a poor immune response
What is a potential risk of live attenuated vaccines?
They have the potential for reversion to virulence
What is a key disadvantage of vectored vaccines?
Repeated use can lead to immunity against vector itself, reducing vaccine effectiveness
What are the key advantages & disadvantages of DNA vaccines?
They provide good T-cell mediated immunity
It is difficult to generate a strong antibody response
What is the DIVA strategy?
Differentiation of Infected from Vaccinated Animals
Diagnostic test used to differentiate infected from vaccinated animals by detecting antibodies to proteins not present in the vaccine
Can’t use DIVA strategy with vaccine containing whole pathogen
What is the mechanism of action of adjuvants?
- Depot Formation – Creates slow-release antigen depot, prolonging immune stimulation
- Secretion of Cytokines & Chemokines – Signals immune cells to enhance response
- Immune Cell Recruitment – Attracts antigen-presenting cells (APCs) to vaccine site
- Antigen Uptake through APCs – APCs engulf & process antigen for immune activation
- Maturation & Activation of Immune Cells – APCs mature & activate T & B cells
- Antigen Processing & Presentation on MHC – Antigens are displayed on APCs for recognition by T cells
- Activated APCs Traffic to Draining Lymph Nodes – APCs move to lymph nodes to interact with naïve immune cells
- Activation of Antibody-Secreting B Cells & CD8+ T Cells – B cells produce antibodies & CD8+ T cells kill infected cells
What are the key steps in ensuring the safety of veterinary vaccines?
Pre-licensing testing (in laboratory animals or target species)
- Safety – Ensuring vaccine doesn’t cause harm
- Efficacy – Demonstrates that vaccine induces immune response
- Effectiveness – Confirms that vaccine prevents disease in real-world conditions
Marketing Authorisation Licence
- Issued by regulatory agencies such as: European Medicines Agency (EMA) & Veterinary Medicines Directorate (VMD)
Post-licensing testing
- Batch-release safety tests – Ensuring each vaccine batch meets safety & quality standards before distribution
What factors contribute to an increased risk of vaccine associated adverse effects?
Small dogs
Neutered
Multiple vaccines on one occasion
What are examples of Type II hypersensitivity reactions to vaccines?
Bovine Neonatal Pancytopenia (BNP) – Linked to Pregsure BVD vaccine
- Caused by alloantibodies attacking calf bone marrow
Chronic Kidney Disease in Cats
- Vaccine viruses cultured in feline kidney cells may lead to renal autoantibody production
What is an example of a Type III hypersensitivity reaction caused by vaccines?
Rabies vaccine-induced cutaneous vasculitis
Causes mild skin reactions & hair loss at injection site
Certain breeds (e.g. Poodles) are predisposed
Describe a type IV hypersensitivity reaction caused by vaccines
Delayed hypersensitivity (days to weeks after vaccination)
Mediated by T cells which produce cytokines
Leads to granuloma formation – fibrous stroma with macrophages, lymphocytes & giant cells around persistent antigen
What are the main reasons for vaccination?
Prophylactic vaccines – Prevent infectious disease in individuals, offspring, or populations
Therapeutic vaccines – E.g.: Oncept melanoma vaccine for dogs to reduce tumors
Immunocontraceptive vaccines – Target GnRH or zona pellucida
Allergen-Specific Immunotherapy (ASIT) – Multiple small doses to achieve immunotolerance
How does herd immunity work?
Depends on the reproduction number (R0) of pathogen
Example thresholds:
Influenza (R0 = 2.0) → 40% vaccinated for herd immunity.
Measles (R0 = 12-18) → 83-94% vaccinated for herd immunity
Why is vaccine effectiveness important for herd immunity?
Coverage needs depend on vaccine effectiveness
E.g.: Equine influenza outbreaks occur when there is mismatch between vaccine strain & circulating strain
Imperfect vaccines may prevent disease but not virus shedding, allowing silent transmission
What is the purpose of boosters?
Antibody level goes up with more exposures
First vaccination IgM & boosters IgG
What are the canine core vaccines?
Canine distemper virus (CDV)
Canine adenovirus type 2 (CAV-2)
Canine parvovirus type 2 (CPV)
Leptospira interogans
What are the canine non-core vaccines?
Bordetella bronchiseptica
Canine parainfluenza virus & Borrelia burgdorferi (kennel cough)
Leishmaniasis
Canineherpesvirus
Rabies virus
What are the feline core vaccines?
Feline parvovirus (FPV)
Feline herpesvirus type 1 (FHV1)
Feline calicivirus (FCV)
What are the feline non-core vaccines?
Feline leukaemia virus (FeLV)
Bordetella bronchiseptica (Bb)
Chlamydophila felis
Rabies
What are the canine vaccination schedules?
Initially: 8 weeks, 12 weeks,1 year & then:
- Distemper (CDV), Infectious hepatitis (CAV) & Canine parvovirus (CPV2) every 3 years
- Leptospirosis every 1 year
Initially: 12 weeks, 1 year & then:
- Kennel cough every year
What are the feline vaccination schedules?
Initially: 8 weeks, 12 weeks,1 year & then:
- Cat flu every 1 year
- FPLV & FeLV every 3 years
What vaccinations are given to rabbits?
Myxomatosis
Rabbit haemorrhagic disease virus (RHDV-1 and -2)
What vaccinations are given to ferrets?
Rabies (travel)
Canine distemper virus – not licensed in ferret
What vaccinations are given to horses?
Depends on use
Equine influenza may be compulsory / required
- Competition animals
- Livery
Equine arteritis for breeding stock
Equine herpesvirus
Strangles
What are the category 1 vaccines in dairy cattle?
Bovine viral diarrhoea (BVD)
Infectious bovine rhinotracheitis (IBR)
Leptospirosis
Bovine respiratory disease (BRD)
Calf scour
What are the category 1 vaccines in beef cattle?
Suckler cows
- BVD
- Leptospirosis
- Clostridial disease
Suckler calves
- Respiratory syncytial virus (RSV)
- Clostridial disease
Growing and feeding cattle
- Clostridial disease
- IBR
What are the category 2 vaccines in dairy cattle?
Salmonella
Ringworm
Mastitis
Lungworm
Clostridial
Arboviruses
What are the category 2 vaccines in beef cattle?
What are the category 1 vaccines in sheep?
Clostridial disease
Footrot
Toxoplasmosis
Enzootic abortion of ewes (EAE)
Pasteurellosis
What are the category 2 vaccines in sheep?
Orf
Ovine Johne’s Disease (Mycobacterium paratuberculosis)
Can vaccines be combined in the same syringe?
Follow manufacturer guidelines
E.g.:
- Nobivac DHPPi can be reconstituted with Lepto-2
- Bovilis Bovipast RSP (inactivated) can be given on same day as IBR Marker Live, but not mixed
What are the different routes of vaccine administration?
Parenteral (injection-based)
- Intramuscular (IM)
- Subcutaneous (SC)
- Intradermal (ID)
- Intranasal (IN)
- Submucosal
Other Routes
- Oral (water-based or bait (rabies vaccine for wildlife))
- Immersion (fish)
- Spray (poultry)
What factors should be considered before vaccinating small animals?
Core vs. non-core vaccines
Age of animal
Pregnancy/lactation status
Medical conditions – Any past vaccine reactions?
Medication use – Some drugs (e.g. immunosuppressants) may reduce vaccine efficacy
What factors should be considered before vaccinating livestock?
Pregnancy/lactation – Some vaccines have meat & milk withdrawal periods
Herd health status – Are there ongoing outbreaks?
Timing of vaccines – Coordinate with calving/lambing
Cost vs. benefit analysis – Is mass vaccination needed?
Handler circumstances (e.g. immune status/pregnancy)
How do equine vaccination rules vary?
Competition horses – Must follow governing body rules
Tetanus – Essential for all horses
Equine influenza –
British Dressage, British Eventing, FEI require specific timing
What is the “immunity gap,” and why is it important for vaccination?
Maternally-derived antibodies (MDA) protect newborns but gradually decline over time
Immunity gap occurs when maternal AB are too low to provide protection but animal has not yet produced sufficient AB on its own
This typically happens between 4-12 weeks of age
Vaccination should be timed within this period to stimulate animal’s immune system before full MDA loss leaves them vulnerable to infection
Why might vaccines be less effective in older animals?
Immunosenescence (aging immune system) leads to:
- Reduced antigen uptake
- Weaker T cell responses
- Impaired memory cell function
“Inflamm-aging” – Older animals have increased chronic inflammation (e.g. IL-6, TNF-α)
How should vaccination protocols change for older cats?
FeLV may not be needed if cat is indoors-only
‘Flu’ (herpesvirus/calicivirus) boosters – Consider annual boosters instead of every 3y
Feline panleukopenia (FPLV) still needed for protection
Older cats have weaker immune systems → disease consequences are more severe
