Download Chapter 21 - Vaccines

Fundamentals of Pharmacology
for Veterinary Technicians
Chapter 21
Vaccines
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
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
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
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
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
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
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
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
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
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
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
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
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
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
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
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 byproducts found in the culture
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
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 single-antigen 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
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
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
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
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
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
Issues in Vaccine Use
• Consider the following with all vaccine
protocols:
– Vaccine issues
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•
•
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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
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
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
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.
Species-Specific Vaccine
Protocols
• Examples of vaccines available for a
variety of species are listed in the
textbook
© 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.