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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: – – – – – – – – 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 • • • • Proper care and handling Proper route of administration Proper use (do not mix vaccine products) Proper dose – Patient issues • • • • • 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.