reactions to vaccination have been recognized for years, and were
commonly seen in several human vaccines including polio and
smallpox vaccines. Adverse reactions to vaccines also occur in
dogs and cats. However, compared to the risks of not vaccinating
dogs and cats, the risks associated with vaccinations are very
small in comparison. Adverse effects from vaccinations can vary
with the type of vaccine used, and the age and breed of animal
vaccinated. Anaphylaxis and the development of a fibrosarcoma are
the most serious reactions to vaccines. Some of the more common
(but still rare) risks are discussed below.
Anaphylaxis is a rare, life-threatening, immediate allergic
reaction to something ingested or injected. If untreated, it
results in shock,
respiratory and cardiac failure, and death. An
anaphylactic reaction can occur as a result of vaccination. The
reaction usually occurs within minutes to hours (less than 24) of
the vaccination. Dr. Ronald Schultz of the University of Wisconsin
College of Veterinary Medicine estimates that about one case of
anaphylaxis occurs for every 15,000 doses of vaccine administered.
The most common symptoms of anaphylaxis are the sudden onset of
diarrhea, vomiting, swelling of the face, shock, seizures,
coma, and death. The animals' gums will be very pale,
and the limbs will feel cold. The heart rate is generally very
fast but the pulse is weak.
Anaphylaxis is an extreme emergency. If you think your dog is
having an anaphylactic reaction, seek emergency veterinary
assistance immediately. Epinephrine should be given as soon as
possible - we are talking within a few minutes. IV fluids, oxygen,
and other medications are given as needed.
Anaphylactic reactions are more commonly associated with the
killed vaccines such as
canine coronavirus, and
leptospirosis. Killed vaccines have more
virus or bacterial particles per dose and have added
chemicals (adjuvants) to improve the dog's immune response. These
characteristics also increase the risk of an allergic reaction to
If your dog has ever had a reaction to a vaccine, subsequent
vaccinations should be given by your veterinarian. In some cases,
certain vaccines may be excluded from your dog's vaccination
regimen, a different type of vaccine will be used, or certain
drugs, including antihistamines may be given prior to vaccination.
The veterinarian may place a catheter in the dog's vein so if a
reaction does occur, medications and fluids can be given
immediately. Depending on the situation, your dog may need to
remain in the veterinarian's office for a period of 30 minutes to
several hours. Once home, the dog should be kept under observation
for several additional hours. Even with these precautions,
life-threatening reactions could still occur.
If you vaccinate your own dogs, you should have epinephrine
available and know how to use it in case a reaction occurs. If
your dog has an anaphylactic reaction after a vaccination, inject
the proper dose of epinephrine and seek emergency veterinary
Worsening of allergies
Some studies have shown that dogs with
atopy who are vaccinated at the height of the allergic season,
may have an increased risk of developing more severe allergy
signs. It is suggested that dogs with seasonal allergies be
vaccinated during the 'non-allergy' season.
Neurologic and eye disease
Neurologic symptoms are the most common vaccine reaction seen
in dogs. Canine
distemper vaccination is the most common cause of neurologic
disease, and can cause an
inflammation of the brain. Measles vaccine in puppies
has been reported to rarely cause damage to the nervous system.
Cerebellar disease has been reported in puppies and kittens less
than 5 weeks of age who were vaccinated with a
modified live vaccine.
Canine adenovirus-1 is known to cause an allergic uveitis
(inflammation of the eye), often called
'blue eye.' Most vaccines now contain canine adenovirus-2
instead of adenovirus-1, almost eliminating the chance of blue eye
Discomfort and swelling at the injection
Pain, swelling, redness, and irritation can occur at the
injection site. These effects generally occur within 30 minutes to
1 week of the vaccination. If the signs persist, or are severe,
contact your veterinarian.
Occassionally, abscesses can form at the injection site. These
abscesses are generally not caused by infection, but by the body's
over-reaction to the vaccine.
Mild fever, decreased appetite and
Mild fever, decreased appetite, and depression may be observed
for 1-2 days following vaccination, most commonly when modified
live vaccines are used. Generally, no treatment is warranted.
Severe illness can occur if vaccines designed for
intranasal use are accidently injected. Severe
reactions can also occur if any of a vaccine made for injection
accidently enters an animal's eyes, nose, or mouth.
Respiratory signs after intranasal
Dogs vaccinated with the intranasal
Bordatella and/or parainfluenza vaccine may develop a
mild cough, which generally does not require treatment. They may
spread the vaccine-form of the virus to other animals through
Rarely, lameness can result from several different
Immune-mediated polyarthritis in Akitas:
Certain lines of Akitas may have
immunodeficiencies which make them prone to adverse reactions
following vaccination. They may develop an immune-mediated
arthritis in one or more joints, which is often progressive and
relapses commonly occur. Dogs with this immune disorder generally
have short life spans due to other complications.
Certain lines of Weimaraners, and some other large-breed dogs, may
hypertrophic osteodystrophy following canine distemper
vaccinations given between 2 and 5 months of age. They may also
develop respiratory signs, enlarged
lymph nodes, and diarrhea. The hypertrophic
osteodystrophy is treated with
glucocorticoids and the signs of the disease usually
Shedding of vaccine agent
Vaccine virus may be found in the nasal secretions of dogs
vaccinated intranasally. In addition vaccine parvovirus is shed in
the feces of vaccinated dogs, canine adenovirus-1 can be shed in
the urine, and canine adenovirus-2 can be found in nasal
secretions. These viruses are the vaccine forms of the virus; they
do NOT revert back to the disease-causing strains.
Birth defects or infections
The vaccination of pregnant animals with a modified live
vaccine can result in birth defects or abortions. It is
recommended that modified live vaccines NEVER be given to pregnant
animals. In addition, vaccinating puppies and kittens less than
4-5 weeks of age, can actually result in them becoming infected
and developing disease from modified live vaccines.
As with any medical procedure, there are always risks of
adverse reactions or side effects. These risks must be compared to
the benefits of the procedure. Many of the diseases against which
we vaccinate can be serious and even lethal. In almost all cases,
the risks associated with vaccination are very small compared to
the risk of developing disease. As new vaccines and methods of
administration become available, the adverse risks of vaccination
should be reduced even more.
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