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Vaccines have been an integral part of preventive health
care programs for several decades now. In fact, no other medical
development has been as successful as vaccination in controlling deadly
diseases in companion animals.
Until recently, recommendations for vaccination of cats and dogs were
fairly unambiguous. As new developments in the field of veterinary
immunology emerge, important questions are being raised about companion
animal vaccines and vaccination protocols. Issues such as whether
veterinarians are vaccinating too often, and related issues such as
adverse vaccine reactions, and whether certain vaccines are efficacious
or not need to be addressed.
There is no consensus on the issues mentioned above. Veterinarians who
deal with unvaccinated animals, or animals with poor vaccination
histories know that canine distemper, feline panleukopenia, and many
other contagious infectious diseases are waiting for the opportunity to
re-emerge. I clearly remember, as a teenager volunteering at a busy
neighborhood veterinary practice, the devastation that the parvovirus
outbreak in the late 70’s brought to the pet dog population. Until an
effective vaccine was developed and marketed, thousands of pet dogs died
terrible deaths from this horrible virus.
Veterinarians, infectious disease experts, researchers, and many clients
have begun to question the need for giving pets yearly booster
vaccinations. The one-year recommendation was not determined by any
scientific studies, and you won’t find in today’s veterinary literature
many publications demonstrating a need for annual vaccination. In 1991,
veterinarians began to notice a higher than expected number of sarcomas,
a type of cancer, occurring on cats’ bodies in places where vaccines
were often injected. Further studies showed that there was an
association between vaccine administration and sarcoma development.
While the incidence of these sarcomas was very low, their occurrence was
devastating to cats that were affected, with many cats dying from these
tumors. It was the discovery of an association between vaccination and
sarcoma development in cats that brought the issue of vaccination to the
forefront of veterinary medicine.
To not vaccinate our pets is not an option. Our challenge is to come up
with a reasonable strategy for vaccination that maximizes our ability to
prevent infectious disease while minimizing the occurrence of adverse
events associated with vaccination.
So, how often should we vaccinate?
It is impractical to recommend a standard vaccination protocol for all
cats. A vaccine risk assessment should be performed yearly for all
cats, and each cat’s individual needs evaluated. Vaccination protocols
should be selected for individual patients based on the risk of exposure
to individual pathogens, incidence of disease, severity of disease,
efficacy and safety of available vaccines, and client-specific requests
and limitations.
The American Association of Feline Practitioners (AAFP) and the Academy
of Feline Medicine (AFM) regularly publish a set of feline vaccination
guidelines for veterinary practitioners to consider. Their guidelines
reflect the most recent studies on vaccine efficacy, safety, and
duration of immunity. Currently, the AAFP/AFM guidelines recommend the
following:
All healthy kittens and adult cats should be vaccinated for life
threatening diseases like panleukopenia, herpesvirus, calicivirus (FVRCP),
and rabies. These are considered the “core” vaccines – ones that every
cat should receive. While vaccines come in a variety of form and
combinations, the most commonly used FVRCP vaccine is a multivalent
vaccine: it contains viral antigens for several diseases. The rabies
vaccine is a monovalent vaccine. It contains viral antigens for
one virus: the rabies virus.
Optional or “non-core” vaccines available for cats include
Chlamydophila felis (a respiratory pathogen, formerly called
Chlamydia), the feline leukemia virus
(FeLV), the feline
immunodeficiency virus (FIV), the feline infectious peritonitis (FIP)
virus, Bordetella (another respiratory pathogen), Giardia (an intestinal
protozoan), and ringworm (a skin fungus). Some of these vaccines are
believed to be fairly efficacious, while others are considered nearly
useless.
Kittens, typically presented to veterinarians at 6 to 8 weeks of age,
should receive an FVRCP vaccine, with additional boosters given every 3
– 4 weeks until 12 weeks of age. Kittens older than 12 weeks of age,
and adult cats with no known vaccination history should receive an FVRCP
vaccine, and one additional FVRCP booster 3 – 4 weeks later.
All cats should receive a rabies vaccine at 12 – 16 weeks of age.
At one year of age, or one year after the last vaccination, an FVRCP and
a rabies vaccine should again be administered.
How often these “core” vaccines should be administered is not entirely
clear. Vaccination is a medical procedure, and like all medical
procedures, it carries some degree – granted, a very small degree – of
risk The goal of veterinarians should be to vaccinate as many cats as
possible, but reduce the number and frequency of unnecessary vaccines.
Some rabies vaccines have been shown to provide immunity for three
years. There is a rabies vaccine currently manufactured that does not
contain some of the irritating substances that have been implicated in
the development of tumors at the injection site. This vaccine, Purevax
(Merial, Ltd) is the only vaccine I use in my feline-only veterinary
practice. This vaccine, however, is only approved for intervals of 1
year. Rabies vaccines that have been shown to give immunity for three
years should not be given any more frequently than this, as it is not
necessary, and only increases the chances of adverse vaccine reactions.
The FVRCP vaccine has been shown, in several studies, to provide
immunity for at least three years, and in many cases, considerably
longer. As a result of these studies, it is now being recommended that
the FVRCP vaccine be given every three years instead of yearly. Even at
three-year intervals, however, some cats would be still be receiving
this vaccination unnecessarily, as some cats retain their immunity to
these virus for longer than three years.
Serology (measuring the level of antibodies against a particular
pathogen) can be used in lieu of an arbitrary vaccine interval for FVRCP
vaccines. Several studies have shown that measuring the level of
antibodies against these viruses correlates well with the degree of
immunity to these diseases. Thus, cats with high antibody levels
against panleukopenia, herpesvirus, and calicivirus are considered to be
protected against these diseases, and therefore do not need to be
vaccinated. Vaccination is indicated only if the antibody level has
dropped to a level that is no longer considered protective.
The serology tests to measure antibody levels against these viruses have
been available for a few years, but veterinarians haven’t taken full
advantage of these tests because the serum samples must be sent to an
outside laboratory. Results can take several days. If the serum sample
shows an inadequate antibody level, the client and cat has to come back
to the hospital for vaccination. This is inconvenient for the client and
for the cat, as most cats get very upset when they go to the veterinary
office, and clients understandably want to minimize the number of visits
if possible. The ideal solution would be a test that can measure the
antibody levels to these three viruses that can be performed right in
the veterinary office, providing answers in just a few minutes while the
client waits.
Once an
in-house serology test becomes readily available, veterinarians and
clients will have more options when it comes to determining the ideal
vaccination schedule for cats. Some veterinarians may continue to
follow the AAFP/AFM recommendations for triennial (every three years)
vaccination, while others may choose to test cats yearly, and vaccinate
only when the antibody levels indicate that it’s necessary.
As stated above,
vaccination against panleukopenia, herpesvirus and calicivirus tends to
be performed using a multivalent vaccines, i.e. a vaccine containing all
three viral antigens in one vaccine dose. If the in-house serologic
test shows the antibody levels for all three viruses to be low, then
this multivalent FVRCP vaccine would be appropriate. But what if the
antibody levels of only one virus, or only two viruses, are inadequate?
Administering a vaccine containing three viral antigens when only one
viral antigen is needed would be considered by some to be
over-vaccinating. Thankfully, vaccine manufacturers have begun
marketing monovalent vaccines - vaccnes containing only one viral
antigen. It is now possible to administer one individual panleukopenia
vaccine, or just the herpesvirus vaccine, or just the calicivirus, or
any combination. Again, this allows veterinarians to fine-tune the
vaccine schedule to the individual cat.
Vaccines against infectious diseases have done much to
reduce sickness and death in companion animals, and vaccination is the
cornerstone of preventive veterinary medicine. As with any medical
procedure or decision, the advantages must be balance against the risks,
and you and your veterinarian should discuss all of the options now
available to determine the best vaccine protocol for your cat.
Related Blog Post:
"Why
We Vaccinate (Even Indoor Cats)"
Updated 4/8/11 |
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