Vaccine Objectives and Qualities

• Vaccines are one of the greatest achievements in preventative medicine, discovered in 1796 by Edward Jenner.
• Jenner found milk maids who got cowpox rarely got smallpox, and used cowpox to produce a vaccine that led to the worldwide eradication of smallpox.

Best Vaccine Qualities

• Mimics the real infection exactly
• Does not cause any signs of disease
• Able to stimulate the immune system like the wild virus or bacteria
• Results in maximum protection with both humoral and cell mediated immunity (CMI)
• Perfectly safe

Vaccine Objectives

• Limits or protects against infection and disease.
• Introduces an antigen into the body to stimulate the production of antibodies by the immune system.
• The principles of vaccination include self versus non-self, protection from infectious disease, and a response indicated by the presence of an antibody.

Clinician's Formula for Clinical Disease

• Includes the quantity of pathogen times virulence of pathogen, divided by quality of immune response
• A vaccine contains an infectious agent, or part of one, recognized by the animal's immune system.
• If the infectious agent is a virus the product is a vaccine; if it contains bacterial components it is a bacterin

Organization of Immune System

• Immunity is separated into adaptive or innate, and natural or artificial
• Natural immunity is either passive (maternal) or active (infection).
• Artificial immunity is either passive (antibody transfer) or active (immunization).

Types of Vaccines

• Killed/Inactivated
• Modified Live/Attenuated
• Attenuated
• Recombinant: Sub-unit, Vectored
• Naked DNA
• Reassortant

Vaccine Terminology

• Epitopes: The specific parts of the antigen that the immune system responds to.
  • The immune system generally responds to many epitopes of a given vaccine.
• Adjuvants: Chemicals used to enhance the immune response to antigens
  • Generally, they produce a longer-lived response.
  • Most adjuvants are used within inactivated or subunit vaccines due to their low immunogenic profile.
  • Live-attenuated vaccines rarely require adjuvants because they usually elicit strong immune responses.
  • Adjuvants have been associated with adverse vaccine reaction fibrosarcomas.
  • Statistically, these reactions occur in ~1:10,000 animals.
• Monovalent: Contains vaccine for only one virus, such as distemper.
• Multivalent: Contains vaccine for more than one virus: distemper, adenovirus, parainfluenza, parvovirus, and leptospirosis.
• Anaphylaxis: An immediate hypersensitivity reaction that manifests within 1 hour post administration of the vaccine.
  • Clinical signs: hives, facial swelling, respiratory distress, severe diarrhea, and shock.
• Vaccine induced sarcomas; more common in felines.
  • Also known as feline injection-site sarcoma (FISS).

Injection Sites for Cats

• R-shoulder: Avoid the midline, distal as possible for FVRCP.
• L-rear limb: Distal as possible for Feline Leukemia Virus.
• R-rear limb: Distal as possible for Rabies Virus.

Task Force Recommendations

• There is insufficient research to recommend a single vaccine type, but recommends vaccination in the lower distal limbs to facilitate clean margins if surgical amputation is required.
• Do not vaccinate in the interscapular space, and do not decrease vaccine volume.
• Distal limb injection is recommended to facilitate amputation with 5 cm margins in two fascial planes in the case of injection-site sarcoma.
• Ventral abdominal subcutaneous injections have been used due to the perceived relative ease of tumor removal without the need for amputation, but the need to remove two fascial planes and 5 cm margins would still necessitate aggressive tissue removal from the abdomen and abdominal cavity.
• Tail vaccination has also been reported as well tolerated, but vaccinations must be administered in the distal tail to facilitate 5 cm margins in the case of injection-site sarcoma,.
• Follow the 3-2-1 rule for postvaccination swelling and obtain incisional biopsies for appropriate diagnosis if:
• The mass remains present 3 months after vaccination.
• The mass is larger than 2 cm in diameter.
• The mass is increasing in size 1 month after vaccination.

Types of vaccines

• Inactivated (non-infectious): Includes killed vaccines.
• Attenuated (infectious): Includes live vaccines with MLV-virus or avirulent-live bacteria.
• Recombinant: Includes virus vectored, subunit, and chimeric vaccines.

Vaccine Creation

• Attenuated: Attenuate (live) through Serial passage.
• Inactivated: Inactivate.
• Subunit: Inactivate, disrupt, and purify.
• Recombinant vaccine: Extract DNA, insert in yeast or bacteria, express antigen, and purify.
• Vectored: Extract DNA and insert DNA into vector.
• Naked DNA.
• Reassortant: Cold adapted "parent."

Feline Vaccines and Their Attributes

Types Of Vaccines

• Inactivated/Killed Vaccines: A vaccine containing killed organisms.
  • Complete inactivation: No replication.
  • Finite antigen mass @ injection.
  • Little cellular or mucosal immunity.
  • Often needs 2 doses.
  • Stable and safe.
  • Destroys infectivity.
  • Less immunogenicity.
  • Requires adjuvant.
• Attenuated: i) Modified Live: Modified living organisms, no longer capable of causing clinical disease.
  • Risk of residual virulence or reversion.
  • Replication amplifies the antigen mass.
  • Humoral, cell mediated, and mucosal immunity.
  • Single dose can be protective.
  • Handling & storage can destroy virulence.
  • Retains infectivity & immunogenicity.
• Attenuated: ii) Avirulent Bacterin: Topical, with rapid onset of local immunity.
  • No maternal antibody interference.
  • Can be administered to dogs and cats younger than 8 weeks of age

Recombinant Vaccines

• Vectored Vaccines: Genes from a pathogen inserted into an attenuated transport microorganism
• Gene-deleted vaccines: Microorganisms with pathogenic genes removed
• Non-infectious subunit vaccines: Only structural components necessary to provoke a protective response

Recombinant Vaccine Advantage

• Have increased efficacy and safety testing results.
• Contain NO adjuvants reduce reaction reports.
• Virus-Vectored Vaccines: Isolates genes that encode for certain proteins.
• Incorporates it into another organism with non disease carrying vectors
• Animal vaccinated with vaccine organisms will express proteins from the original pathogens
• Leads to immune creation of antibodies
• Induces humoral and T-cell mediated response similar to modified live vaccines
• Sub Unit Vaccines: Contains particular / non-disease causing proteins from the pathogen DNA.
• Antibodies are created in the animal, the immune system recognizes different proteins needed to manufacture.
• The gene is inserted into a different organism, usually bacterial.
• Require reduced levels of antigen for immune stimulation
• Chimeric Vaccine: unique, nonconventional and new-generation veterinary vaccines, that can be constructed by combining multiple polyvalent antigens

Toxoid Vaccines

• Toxoid vaccines are made from selected toxins (proteins) that are sufficiently attenuated and rendered harmless to induce a humoral immune response.
• Leads to poor DOI with multiple doses or boosters.

Why Vaccines Fail

• Vaccine Failure Reasons:
  • Incorrect Administration
  • Death of the Live Vaccine
  • Passive Protection
  • Incorrect Route (Inappropriate)
• The Animal Fails to Respond:
• They are already Infected
• The Wrong Strain was given
• The Vaccine contains nonprotective Antigens

Contributing factors to vaccine failure

• Prior passive immunity
• Patient Immunosuppression
• Inadequate Vaccine storage

Types of Rabies Vaccine

• One year vaccines versus Three year vaccines:
  • Both types are available
• The Three year vaccine still requires an initial vaccine, followed by the first annual booster.

Core Vs Non Core Vaccinations

• Core:
  • Severity of disease
  • Transmissibility
  • Potential for infection
• Noncore:
  • Recommended to clientele when animal is known or likely at risk after reasonable exposure to infectious agents.

Types of Core & Noncore Vaccines

• Core vaccines: Rabies, canine distemper, canine adenovirus type I, canine parvovirus, leptospirosis.
• Noncore vaccines: Bordetella, leptospirosis, Lyme, coronavirus, giardia

Core Vaccines: Cats

• Rabies
• Feline Viral Rhinotracheitis
• Feline Calicivirus
• Feline Panleukopenia
• FeLV

Non-Core Vaccine: Cats

• FIV, FIP , corona
• Chlamydia
• Bordetella
• Ringworm
• Giardia

Vaccine Banks

• Vaccine Banks: National Veterinary Stockpile (NVS).
  • This is for approved vaccines for important animal diseases that are not currently present in the country's borders.
    • Can be deployed within 24 hours.
    • Expensive to maintain.

Alternative Vaccines

• Owners' concerns:
  • Immune system overload
  • Vaccine induced disease
• Global estimates in developed countries is that 30-50% of pet population is vaccinated.
• No vaccine is 100% effective, and do not induce the same degree of protection in every single animal.