Pet vaccinations are responsible for preventing countless numbers of pets from suffering from serious infectious diseases. Vaccinations are still considered the cornerstone of preventive medicine. However, unlike the past when vaccinating a pet was considered to be a beneficial medical procedure with very little risk of adverse reactions, today the veterinary profession knows that adverse reactions are possible with any vaccination. This discovery has led to major changes in the way vaccines are administered to pets.
How Pet Vaccines Work
Vaccinations protect pets against disease by allowing pets to mount a protective immune response before exposure to the disease. Vaccines may function by providing
- a live form of the infectious agent which has been modified so that it does not produce disease,
- a killed form of the infectious agent which also is incapable of causing disease, or
- a portion of the infectious agent which, by itself, is not capable of causing disease.
These different types of vaccines all act by allowing the animal to react to the vaccine immunologically in a way which provides protection to the pet against the actual disease. It should be noted that some vaccines (such as the intranasal Bordetella vaccine) may actually cause mild disease symptoms for the pet but also still produce immunity against more serious disease.
Normal Pet Vaccine Reactions
Though many pets undergo vaccination with no ill effects, it is not unusual to see mild symptoms after vaccination. These symptoms may include:
- mild fever
- listlessness
- lethargy
- mild swelling at the injection site
- mild discomfort at the injection site
These symptoms are normal and should not cause alarm for the pet owner after vaccination.
Abnormal Pet Vaccine Reactions
In some instances, pets may mount an abnormal immune response after vaccination, known as an anaphylactic or allergic reaction. Symptoms may include:
- vomiting
- swelling of the face and/or eyelids
- itchiness
- rash or "hives"
These reactions are rare and usually occur within 48 hours after vaccination. These reactions can become life-threatening, especially if left untreated.
Feline Sarcomas and Vaccinations
Another adverse reaction which has been recognized in relation to vaccination, primarily in cats, is the formation of a specific type of tumor, known as a sarcoma. Sarcomas are known to be extremely locally invasive and aggressive in nature. Fortunately, vaccination sarcomas are rare, with the current estimate being less than 1 in 10,000 cats being affected, according to a study published in the Journal of the American Veterinary Medical Association by Drs. GE Moore et al (Vol. 231, 2007).
Reasons for Vaccinating Pets
Though it is recognized that vaccinations can cause adverse reactions in pets, it is also well recognized that many of the diseases routinely vaccinated against can still cause serious and even fatal disease in pets. In addition, some of these diseases also pose a threat to people and protecting pets against these diseases can also help to protect pet owners and the general public.
Balancing the Risk of Adverse Vaccine Reactions with the Risk of Disease Exposure
There are several considerations which must come into play when considering whether vaccinating a pet is the right decision.
Firstly, new technology has created vaccinations which are safer for pets and these should be utilized by the veterinarian administering the vaccine.
Secondly, consideration of the risk of exposure to disease is important. Pets which are not at risk for a particular disease need not receive a vaccination against that disease. Vaccinations for pets are now divided into core and non-core vaccinations.
- Core vaccines are those which protect pets against diseases which are considered to be wide-spread and/or serious enough to warrant consideration for all pets. Even with core vaccinations, an individual risk assessment should take place when deciding whether or not to vaccinate.
- Non-core vaccinations are those vaccines which protect against diseases which are more likely to be encountered by specific populations of pets. In considering the necessity of vaccinating against non-core diseases, a risk assessment for each individual animal must be performed and those animals at low or no risk of disease should not receive the vaccine.
Vaccinating pets has become a complicated subject with many considerations that must come into play. Very basically, vaccination schedules must be tailored to meet the needs of individual pets based on their life style and their risk of encountering specific diseases. In some cases, risks imposed by vaccination may outweigh the risk of the pet actually getting the disease. In these cases, vaccination is not indicated. In other cases, risk of exposure to the disease and the illness which may result may pose a greater threat to the pet than administering the vaccination. In this case, vaccination is recommended and, in some cases, may even be mandatory, as with vaccination against rabies.
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