These are produced by deleting virulence genes from a pathogen while protective antigens are left in place. or protection from infectious disease and may be or involves administration of vaccines that stimulate cell-mediated or humoral immunity, or both, to a specific pathogen. refers to the administration of antibodies in order to provide temporary protection from disease and can occur through acquisition of maternally derived antibody (MDA) transplacentally, in colostrum, or milk; or treatment with preparations that contain specific or nonspecific immunoglobulins (see Immunomodulators, Chapter 7, and post-exposure prophylaxis for rabies, Chapter 13). Readers are referred to advanced immunology texts for detailed descriptions of the physiology of active and passive immunity.1 The goal of immunization is to generate a protective immune response of prolonged duration against a specific infectious disease, with minimal adverse effects. Because of the potential for adverse effects, vaccination should be performed only if there is a risk for significant morbidity or mortality from an infectious disease. Since the 1950s, a huge number of vaccines for dogs and cats have been developed and marketed worldwide, and Erlotinib HCl more are in development. Nevertheless, it is estimated that even in developed countries such as the United States, only 30% to 50% of dogs are properly immunized, and possibly an even smaller proportion of cats.2., 3. Appropriate vaccination of a larger proportion Erlotinib HCl of the pet population may assist in reduction of the prevalence of infectious diseases through the induction of herd immunity. With the appearance of injection-site sarcomas in cats, increased emphasis has been placed on vaccine safety, and a change from annual to 3-yearly immunization protocols for some vaccines has been recommended, with administration of other vaccines based on exposure risk. Vaccines have had a profound influence in the control of infectious disease, and for many vaccines the benefits of vaccination outweigh the risks. Vaccine Composition and Types of Vaccines A vaccine is a suspension of attenuated live or inactivated microorganisms, or parts thereof, that is administered to induce immunity. Erlotinib HCl In addition to protective antigens, vaccines may contain preservatives and stabilizers as well as specific antibiotics to preserve the antigen and inhibit bacterial and fungal growth within the vaccine. Some vaccines also contain an to enhance the immune response to the antigen. Although the mechanisms are not completely clear, adjuvants can delay the release of antigen from the site of injection and induce the secretion of chemokines by leukocytes.4 The most widely used adjuvants are particulate adjuvants, such as those that contain aluminum salt precipitates such as aluminum hydroxide.5 Other particulate adjuvants include immunostimulators such as saponin, which is present in a canine vaccine. (or modified live vaccines) contain microorganisms that are artificially manipulated so as to negate or greatly reduce their virulence, or are field strains of low virulence. Repeated passage through cell culture is the most common means of attenuation. Because they replicate in the host, organisms in attenuated live vaccines usually stimulate an immune response that most closely mimics the protection that results from natural infection. Vaccination with attenuated live canine parvovirus (CPV) and canine distemper virus (CDV) vaccines in the absence of MDA can result in protective immune responses within 3 days of a single injection, which may be followed by immunity that lasts Rabbit polyclonal to F10 many years, if not for life.6., 7., 8. Partial immunity after vaccination with attenuated live CDV and feline panleukopenia virus (FPV) vaccines can occur within hours.3., 9., 10. In addition, vaccine organisms that are shed can serve to immunize other animals in a population. However, the potential for reversion to virulence or vaccine-induced disease exists. Vaccine-induced disease is most likely to occur in highly immunosuppressed animals. Attenuated live vaccines also have the potential to cause some immunosuppression in their own right,11., 12. or they may Erlotinib HCl shift the balance.