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Chapter 21
Vaccines
Copyright © 2011 Delmar, Cengage Learning
Immunity
• Nonspecific immunity
– Includes things such as physical barriers, mucus
production, inflammation, fever, and phagocytosis
– Directed against all pathogens; is the initial defense
against invading agents
• Specific immunity
– Takes over when the nonspecific mechanisms fail
– Targeted for a specific antigen; has memory
– Arises from B- and T-lymphocytes
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Types of Immunity
• Cell-mediated immunity
– T-lymphocytes directly attack the invading antigen
– Important for protecting against intracellular bacterial
or viral infections, fungal diseases, and protozoal
diseases
• Antibody-mediated immunity
– B-lymphocytes produce antibodies that react to
antigen
– Important for extracellular phases of systemic viral
and bacterial infections and protection against
endotoxin and exotoxin-induced disease
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Ways to Acquire Specific Immunity
• Active immunity
– Arises when an animal receives an antigen that activates B- and
T-lymphocytes
– Creates memory
• Passive immunity
– Arises when an animal receives antibodies from another animal
– Provides immediate onset of immunity, but the animal is
protected for a shorter time (no memory)
• Natural immunity
– Acquired during normal biological experiences
• Artificial immunity
– Acquired through medical procedures
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Vaccines
• A vaccine is a suspension of weakened, live, or killed
microorganisms administered to prevent, improve, or
treat an infectious disease
• Types of vaccines:
– Inactivated (killed): made from microbes, microbe parts, or
microbe by-products that have been chemically treated or
heated to kill the microbe
• Contain adjuvants (substances that enhance the immune response
by increasing the stability of the vaccine in the body); may cause
vaccine reactions
• Advantages: safe; stable; unlikely to cause disease
• Disadvantages: need repeated doses; possible reactions
Copyright © 2011 Delmar, Cengage Learning
Vaccines
• Types of vaccines (cont.):
– Attenuated (modified-live): microorganisms go
through a process of losing their virulence (called
attenuation), but must be able to replicate within the
patient to provide immunity
• Advantages: immunity lasts longer; has better efficacy and
quicker stimulation of cell-mediated immunity than killed
vaccines
• Disadvantages: possible abortion; can produce mild forms of
the disease; can shed into the environment; proper
handling/storage is critical
Copyright © 2011 Delmar, Cengage Learning
Vaccines
• Types of vaccines (cont.):
– Live: made from live microorganisms that may be fully
virulent
• Advantages: fewer doses needed; last longer; inexpensive;
adjuvants not needed
• Disadvantages: residual virulence that requires carefully
handling
– Recombinant: a gene or part of a microorganism is
removed from one organism (usually the pathogen)
and inserted into another microorganism
• Advantages: fewer side effects; effective immunity; varied
routes of administration
• Disadvantage: increased cost
Copyright © 2011 Delmar, Cengage Learning
Vaccines
• Types of vaccines (cont.):
– Adjuvants: substances that enhance the immune
response
– There are four types of adjuvants:
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Depot
Particulate
Immunostimulatory
Mixed
– Depot adjuvants protect antigens from rapid
degradation which contributes to a prolonged immune
response
Copyright © 2011 Delmar, Cengage Learning
Vaccines
• Types of vaccines (cont.):
– Particulate adjuvants deliver antigen in such a way
that both cell-mediated and humoral immunity are
enhanced by stimulation of antigen processing
– Immunostimulatory adjuvants promote cytokine
production
– Mixed adjuvants combine a particulate or depot
adjuvant with an immunostimulatory agent
Copyright © 2011 Delmar, Cengage Learning
Vaccines
• Types of vaccines (cont.):
– Polyneucleotides: or DNA vaccines injects DNA that
encodes for foreign antigens is another type of
vaccine
• Advantage: that it is possible to select only the genes for the
antigen of interest
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Vaccines
• Types of vaccines (cont.):
– Toxoids: “vaccine” used against a toxin that has been
deactivated by heat or chemicals, but is still able to
stimulate antibody production
• Advantage: provides protection against toxin
• Disadvantages: shorter duration of effectiveness; may
contain adjuvants
– Antitoxins: substances that contain antibodies
obtained from an animal that has been
hypersensitized to neutralize toxins
• Advantage: quick protection against a toxin
• Disadvantages: short-lived protection; may contain
preservatives that can cause reactions
Copyright © 2011 Delmar, Cengage Learning
Vaccines
• Types of vaccines (cont.):
– Antiserum: antibody-rich serum obtained from a
hypersensitized or actually infected animal
• Advantage: provides quick protection against a
microorganism
• Disadvantages: shorter duration of effectiveness; may
contain adjuvants
– Autogenous: vaccine produced for a specific disease
in a specific area from a sick animal
• Advantage: provides protection against the specific organism
in a specific area
• Disadvantage: may contain endotoxin and other by-products
found in the culture
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Vaccines
• Types of vaccines (cont.):
– Multiple-antigen vaccines are called polyvalent
– Polyvalent vaccines contain more than one antigen
• Contain a mixture of different antigens and are more convenient to
administer because fewer injections are needed
• Adverse reaction increases as the number of antigens increases
– To be approved, must show that each part of the polyvalent
vaccine induces the same level of immunity as does the singleantigen vaccine
– Monovalent vaccines are vaccines with only a single antigen
present
• Using several monovalent vaccines may expose the animal to
higher levels of adjuvants
• Must give more injections
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Maternally Derived Antibodies
• Maternally derived antibodies are antibodies that
offspring receive passively from their mothers, either
from colostrum or via the placenta
• Maternally derived antibodies give the offspring disease
resistance for a few days and provide variable antibody
levels for up to nine weeks
• To enhance this protection, young animals receive
vaccinations and booster vaccinations to ensure
appropriate immunity
– Booster vaccines are needed because effective vaccination
varies among individuals, because of variable levels of maternal
antibodies
– Booster vaccines also allow antibody levels to rise to satisfactory
levels
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Vaccine Reactions
• Although vaccines are considered safe, vaccine
reactions can occur
• All vaccine reactions must be recorded in the medical
record
• Typical vaccine reactions:
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Location reactions at the injection site
Fever
Lethargy
Vomiting
Salivation
Difficulty breathing
Vaccine-associated sarcomas in cats
Autoimmune hemolytic anemia in dogs
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Issues in Vaccine Use
• Consider the following with all vaccine protocols:
– Vaccine issues
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Proper care and handling
Proper route of administration
Proper use (do not mix vaccine products)
Proper dose
– Patient issues
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Animal age
Freedom from disease
Concurrent use of medication
Pregnancy
Environment
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Vaccine Protocols
• Practice of annual vaccination is now under debate
• One way to discover when revaccination is necessary is
via the antibody titer
– An antibody titer is a serum test that reveals the level of antibody
to a particular antigen in a particular individual
– Antibody titers are expressed as 1:2, 1:4, etc., a ratio that
represents the dilution at which the immune response is still
adequate
• Core vaccines are recommended for all individual
animals
• Noncore vaccines are recommended only for individual
animals deemed to be at high risk for contact with the
organism
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Species-Specific Vaccine Protocols
• Examples of vaccines available for a
variety of species are listed in the textbook
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