This NebGuide explains the basics of vaccine value, the differences between types of vaccines used in animals, and discusses vaccine selection and vaccination program development.
Dave Smith, Extension Veterinarian; and Grant Dewell, Clinical Veterinarian
- Vaccine Terms
- Vaccine Types
- What Should Be Expected From Vaccines
- Factors That Influence Vaccine Selection
- Why Vaccines Fail to Work
>>>>>>> 1.5 Vaccines are an important part of disease prevention and control. Like insurance, vaccines come at a cost, including the price of the vaccine, labor to administer the vaccine, localized tissue damage from vaccine injections, and <<<<<<< g1445.htm increased metabolic demand of the animal causing potential performance loss during the time the animal is developing a proper immune response. The increased metabolic demand can cause the animal to look depressed and therefore may be confused with illness. This is sometimes referred to as “vaccine sweat.” If the risk of a particular disease is low, the insurance afforded by vaccination may not be required and the benefit provided might not be cost effective. If the risk of disease is high, the insurance afforded by vaccination may be very cost effective even if it does not completely prevent sickness. It is important to view vaccines only as an aid to health management and not the foundation of animal health.
======= increased metabolic demand of the animal causing potential performance loss during the time the animal is developing a proper immune response. The increased metabolic demand can cause the animal to look depressed and therefore may be confused with illness. This is sometimes referred to as “vaccine sweat.“ If the risk of a particular disease is low, the insurance afforded by vaccination may not be required and the benefit provided might not be cost effective. If the risk of disease is high, the insurance afforded by vaccination may be very cost effective even if it does not completely prevent sickness. It is important to view vaccines only as an aid to health management and not the foundation of animal health. >>>>>>> 1.5
Antigen: A substance that when introduced into the body stimulates the production of an antibody.
Antibody: A specific disease protection protein produced by the animal’s body in response to contact with disease causing organisms or vaccine.
Adjuvant: An immunological agent that enhances the immune response to a vaccine.
Endotoxin: A bacterial cell wall component released when bacteria die that is able to cause collapse of several animal physiologic processes (Endotoxic Shock). Endotoxin can be a problem in poorly manufactured killed bacterial vaccines or when multiple bacterial vaccines are given at once. Frequently the endotoxin level in autogenous bacterial vaccines is high and therefore should be used with caution. Ask your veterinarian for more information on this subject.
Interferon: A protein produced by cells in response to infection by a virus that acts to prevent viral replication and have the ability to induce resistance to viral antigens.
Active immunity: Immunity produced in response to a disease organism or vaccine.
Passive immunity: Immunity, usually antibodies, acquired from colostrum or anti-toxins. Although duration of activity is brief (weeks to months), it is critical to the health of young animals. While present, passive immunity may interfere with the immune response to a vaccine. Colostrum provided to infants is the most common example of acquired passive immunity.
Intramuscular (IM) Injection: An injection given in the muscle. The size (length and diameter) of the needle used should be appropriate for the animal.
Subcutaneous (SQ) Injection: An injection given between the skin and underlying muscle. SQ is the preferred route of administration for all vaccines given to food producing animals because of the damage done by IM injections to edible tissue. This is especially true of killed vaccines that contain an adjuvant such as aluminum hydroxide or oil. Because SQ injections cause less damage to muscle, it is reasonable to think SQ administration is more humane and could improve animal performance.
Intranasal (IN) Administration: Aerosolized product delivered through the nasal cavity.
Subunit vaccines are a type of killed vaccine that contains only part of the virus or other microorganism. These vaccines were developed to either isolate or engineer the most important part of the microorganism needed to produce a proper immune response and eliminate the part(s) of the microorganism that caused adverse vaccine reactions or interfered with a proper immune response.
Autogenous bacterial vaccines (Autogenous Bacterins) are produced from disease causing organisms isolated from sick animals. The disease causing bacteria are grown in culture, killed and mixed with an adjuvant. These vaccines frequently contain high levels of endotoxin and other by-products found in the culture (debris). Because autogenous vaccines frequently contain high levels of endotoxin and other by-products found in the culture (debris), they should be used with caution.
Modified live vaccines (MLV) contain a small quantity of virus or bacteria that has been altered so that it no longer is capable of causing clinical disease but is still capable of infection and multiplying in the animal. Recognition of the replicating organism by the animal’s immune system results in an enhanced immune response. The immunity produced by MLV typically lasts longer than the immunity produced by killed vaccines. Handling and storage of MLV products is critical. Exposure to high temperatures, sunlight, freezing temperatures, disinfectants or soaps can damage or destroy a MLV product. MLV products require rehydration of lyophilized vaccine cake with provided diluent and should be used within an hour of mixing. The major advantage of modified live vaccines is a broader scope and duration of protection because the animal is exposed to all stages of the replicating virus or bacteria.
Chemically altered vaccines contain modified live organisms that have been grown in a media containing adjusted levels of certain chemicals that trigger and amplify mutation of the organism, changing the organism’s metabolism in such a way as to alter the ability to cause disease. Temperature sensitive (TS) vaccine organisms are examples of an organism produced by this process. The TS organism loses the ability to grow at the animal's normal body temperature but can grow at the temperatures present in ocular or nasal mucosa. Chemically altered organisms are considered safer than typical modified live organisms, but when given by a route other than direct contact with the mucus membranes stimulate little or no local immunity. The immune response produced is similar to MLV products but the duration of immunity is not considered to be as long. The major advantage of chemically altered vaccines is they are safe to use with pregnant animals because there is no systemic replication of the vaccine organism.
|Figure 1. Vaccine types: advantages vs disadvantages.
Lastly, the cost of vaccination should be less than the economic loss incurred by the naturally occurring disease. The cost of vaccination should consider the long-term effects of the disease and long-term economic losses. Vaccines should not be expected to eliminate all disease problems. Many additional management procedures such as animal density, nutrition, environmental control, movement of animals, levels of stress, cleanliness of the environment, cleanliness and availability of drinking water, and the number of different disease-causing organisms in the environment can all influence how well a vaccine will work.
However, combination vaccines may not always be appropriate. It may be advantageous to give BVD and Hemophilus somnus in separate injections rather than in one combination injection. This allows the H. somnus vaccine to be given SQ, avoiding damage to eatable tissue caused by the aluminum hydroxide adjuvant. Vaccines are production management tools and are not a substitute for proper animal husbandry. Production management factors need to be considered. The objective should be disease prevention through total production management including appropriate biosecurity (Figure 2). However, if there is a breakdown in production management and a disease outbreak occurs, the vaccination program (insurance) needs to be adequate and effective to limit resulting losses. Thoroughly understanding causes of vaccine failure will help prevent future problems.
Interference with a vaccine’s ability to stimulate immunity is most commonly linked to pre-existing antibody from either a previous vaccination or passively acquired antibody from colostrum. Other causes of interference or immunosuppression include handling stress, weather stress, preexisting disease, parasitism, malnutrition, pregnancy, and steroid treatments.
Stress can lead to immune suppression and may reduce the animal’s ability to mount an immune response. Stress could include environmental extremes, handling, inadequate nutrition, parasitism, and other diseases. While it is common to vaccinate stressed animals, these animals are more susceptible to adverse vaccine reactions and frequently do not develop an adequate immune response. Immune stressed animals develop limited protection from vaccination. Frequently high stressed animals may be incubating disease at the time of vaccination. Although the subsequent sickness and death loss mimics a vaccine reaction, the underlying disease is to blame. Unless using the vaccine to stimulate immediate partial immunity, delaying vaccination of stressed animals is advisable. Similarly, properly vaccinated animals may still contract a disease if they are later stressed.
Existing antibodies to the antigen(s) contained in the vaccine can block vaccine response. Antibodies acquired through colostrum at birth are critical to the newborn’s health, but only last three to six months and while present can block the immune response to a vaccine. This is referred to as Passive Antibody Interference or Maternal Interference.
Improper timing of vaccination is a common cause of vaccine failure. If an animal is incubating disease at the time of vaccination, the underlying disease may not be prevented by the vaccine. The clinical signs may mimic an adverse vaccine reaction although the symptoms are really due to a previous infection. An animal can succumb to a disease if exposed to the natural infection following vaccination before it has had time to develop an adequate immune response. The protection afforded by vaccination cannot be expected until the immune response is complete. After the first exposure to an MLV product, interferon (a nonspecific protective protein) levels rise within hours followed by antibodies detectable in approximately four to five days. Killed vaccine products require training the immune system by two vaccinations given not less than 10 days apart. With KV products the immune system is not ready to protect the animal until after a rise in antibodies following the second vaccination.
Similarly, an animal can succumb to a disease if exposed to the natural infection following vaccination if the length of time between vaccination and exposure has been longer than the protection afforded by the vaccine. Most vaccines do not ensure lifelong immunity from one or two injections.
The protection afforded by a vaccine may also be incomplete if the vaccine does not contain the proper strains or serotypes of organism required to stimulate protective immunity. Although the vaccine is administered properly and the immune system responds appropriately, the animals can still exhibit clinical signs of the disease, particularly if the animals are stressed or exposed to an overwhelming level of infectious agents. There are additional disease-causing organisms present in the environment that are not commercially available in vaccines.
<<<<<<< g1445.htm Vaccine may be of poor quality (low vaccine titer, contaminated, etc.). The vaccine manufacturing industry is highly regulated by the USDA-APHIS and major manufacturers have extensive quality control programs. Vaccine failure due to faulty vaccine manufacture is rare. USDA approved vaccines will be safe and effective if used properly. In some situations, one type of vaccine may be better than another. Choosing the correct vaccine and using it properly is an important part of preventative animal health.
Visit the University of Nebraska–Lincoln Extension Publications Web site for more publications.
Visit the University of Nebraska–Lincoln Extension Publications Web site for more publications.