The Role of Vaccines
Vaccines are developed with the aim of providing immunity against disease. Vaccinating animals for disease prevention has become common practice among both pet owners and livestock producers. For our pets, vaccines are administered by the veterinarian as part of routine visits.
Livestock producers consult with their veterinarian to select from the broad range of vaccines now available to provide immunity against specific diseases that threaten their animals. As a result of their proven effectiveness, vaccines are a major component of animal health management programs which focus on disease prevention. Vaccines are often administered by livestock producers following guidelines from their veterinarians.
What are Vaccines?
Vaccines may contain killed (bacterins) or live bacterial components, inactivated viral components, or modified live viral components which are either alone or in combinations. Some also contain inactivated toxins called toxoids. Vaccines are administered by a variety of methods such as injections under the skin or application into the nostril, all sharing the same goal – to induce some form of immunity against disease.
Many products can be used to provide an immune response. Listed below are these additional classes of immunity-inducing products:
- Bacterins contain inactivated bacterial components.
- Toxoids contain inactivated toxins.
- Antitoxins and antisera contain antibodies against toxins or the germ itself.
- Polyclonal and Monoclonal antibodies contain antibodies that are specific for various infections.
- Immunostimulants contain biological substances which stimulate lymphocytes (white blood cells involved in the immune response).
How Do These Products Work?
They work in different ways. Vaccines, bacterins and toxoids work by urging the animal to ‘turn on’ its own immune system to respond to a specific germ – mainly by producing antibodies. By giving the animal early exposure to the infectious germ, the animal’s immune system is also stimulated to "remember" the agent and is therefore better able to quickly resist that germ when re-exposed sometime in the future.
Immunostimulants are designed to amplify an animal’s immune response to better deal with an impending disease threat. Antitoxins and polyclonals contain antibodies already made and are therefore able to provide an instant source of resistance to help minimize the effects of an imminent disease.
Planning Ahead Gives Maximum Protection
A very important aspect of vaccination is the time between injection and development of protective immunity. In most cases, with killed vaccines, two primary vaccinations are required to induce a sufficient level of protection and longevity of immunity. The first vaccine, the sensitizing dose, only primes the immune system and rarely induces adequate immunity by itself. A second vaccine, or booster, is required to increase an animal’s level of immunity to the satisfactory level. Most modified live vaccines, however, are able to stimulate the immune response after only one dose.
An animal is considered to be immunized a week or two after the booster is administered. In other words, a vaccination program should be completed a week or two before exposure to the particular germ is expected.
Can You Expect 100 Per Cent Protection?
Not always. The effectiveness of a vaccine in inducing immune protection can be affected by many variables such as nutrition, stress, and subclinical infection. Whether or not the animal contracts a disease depends on the animal’s level of immunity at the time of exposure compared to the level of exposure to the infectious agent.
In most cases, the increased level of immunity induced by vaccination should be sufficient to fight off the disease. However, animals that are sick at the time of vaccination or under severe stress when exposed to the disease-causing agent, may not mount a protective immune response to any vaccine(s) they are given and may therefore not have sufficient immunity to resist infection.
Supportive Care Helps Maximize Immunity
While a vaccine increases an animal’s level of immunity, it won’t necessarily provide complete protection for your pet or livestock. The supportive care that you provide can help to maximize immunity and minimize disease exposure. Supportive care includes good nutrition, proper housing, fresh water, proper ventilation and a clean environment.
Are Vaccines Licensed for Use in Canada?
All vaccines offered for sale in Canada must be registered with the Canadian Centre for Veterinary Biologics, Canadian Food Inspection Agency. Vaccines are cleared for use only after veterinarians and scientists within this federal government department review data on purity, potency, safety and efficacy.
Vaccine Precautions
Administering any foreign material always presents some risk of side effects. With vaccines, the risks are often minor and have to be measured against the potential risk of contracting the disease.
Here are a Few Vaccine Precautions:
- Localized swelling may occur at the injection site. This is typically related to adjuvants used in the product (to slow down absorption of the product to increase the immune response).
- In rare cases, animals may become hypersensitive to components in a vaccine. Over-reaction of the immune system may result in a localized reaction or a more serious generalized reaction. Any vaccinated animal should be monitored closely for the first hour after receiving a vaccine or other immune stimulant. If any abnormal reaction is observed, call your veterinarian immediately. Producers who administer their own vaccines should ask their veterinarian about the use of drugs to reverse severe allergic reactions.
- Modified live virus vaccines contain components that are safe as long as label directions are followed closely. For instance, "not for use in pregnant animals" demands strict adherence.
- Animals that are too young should not be vaccinated. Depending on the species and the vaccine, the young animal’s immune system may not be sufficiently developed to respond. In some cases, the mother’s antibodies received by the young animal through consumption of colostrum may interfere with or cancel the effects of a vaccine.
- Vaccines should not be mixed together in the same syringe as this may inactivate the vaccine or cause it to become more reactive.
- Special care must be taken in handling live viral and bacterial products as they are susceptible to inactivation. Follow directions carefully and avoid exposing the vaccines to disinfectant agents.
If you have questions on specific vaccines or products, consult you veterinarian.
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