Adverse
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
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 use of
killed vaccines
such as rabies, 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 the vaccine.
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 assistance immediately.
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
occurring today.
Discomfort and swelling at the injection site
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.
Occasionally, 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 activity
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 accidentally injected. Severe reactions can also
occur if any of a vaccine made for injection accidentally
enters an animal's eyes, nose, or mouth.
Respiratory signs after intranasal vaccines
Dogs vaccinated with the intranasal
Bordetella
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 their coughing.
Lameness
Rarely,
lameness can result from several different vaccinations.
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.
Hypertrophic
osteodystrophy:
Certain lines of Weimaraners, and some other large-breed
dogs, may develop
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 resolve.
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.
Summary
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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