How Do Vaccines Protect my Cat

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Cat vaccination
Cat Vaccination

Recent years have brought much discussion among veterinarians, breeders, and cat owners on the value, safety, and necessity of some vaccines. The resultant rumors mixed with fact have caused concern among cat lovers: Does my cat really need to be vaccinated every year? Are vaccines more harmful than helpful?

I ran into this kind of dilemma in 2015 when facing a move 2,600 miles from California to Georgia, which requires rabies vaccines in all dogs and cats. Rabies vaccines are also required in many of the states we drove through along the way. In that instance, we consulted with our trusted veterinarian, and based on her input, had all six of our cats vaccinated for rabies.

Unfortunately, there is no one answer that would be applicable to all cats, but with a better understanding of the facts, you can work with your own veterinarian to work out a vaccination scheme that will provide the safest protection for your cat.

black cat across green-leafed plants photo
black cat across green-leafed plants photo

How Do Vaccines Protect my Cat?

Vaccines do not inject a miraculous shield against disease. They work by fooling the body into thinking it is threatened, thereby stimulating the body's own defense system into producing antibodies to fight off the invader. Vaccines are made from either killed viruses or live viruses that have been altered to not cause disease (modified live or MLV), and can be given individually, although some serums are often given as a group (multivalent), e.g. the 3-Way, or FVRCP.

Vaccines are most commonly given by injection, although several new intranasal vaccines have been developed.

After the initial first vet visit, and kitten shots, boosters are given to boost the cat's defense system. Traditionally, veterinarians have asked owners to bring their cats in for annual boosters, along with their annual well-cat checkup, however, times are changing and many veterinarians are moving to an every three year protocol, with some exceptions.

white and black cat lying on grass
white and black cat lying on grass

Beginning in the late 90's, there was concern about vaccines in cats causing tumors at the injection sites. These were originally termed vaccine-associated feline soft tissue sarcomas. Though rare, these tumors were serious, so a task force was developed to research the cause. Ultimately it was discovered that many types injections can cause these tumors, not just vaccines, and they were renamed injection site sarcomas. It was not the vaccines themselves causing the problem, but the inflammation caused by the needle stick. For this reason, a move towards using three year vaccines has occurred. It is also recommended that vaccines be given as low on the leg as possible, or on the tail, so that these tumors can be more easily treated if they do occur.

Live VS Killed Vaccines

FVRCP vaccines are available in either version, and your veterinarian will be able to select the appropriate one for your cat, based on his health history. MLVs are generally preferred in most cases, but you'll want to discuss this matter thoroughly with your veterinarian.

Rabies vaccines are only available as killed viruses.

orange and white cat on grass in macro photography
orange and white cat on grass in macro photography
  • Modified Live Vaccines (MLV): MLVs basically do their own dirty work, in fooling the body into believing it has an outsider invader, thus encouraging it to create antibodies against the antigen. MLVs are believed to give a higher-quality immune response than that available from killed viruses. The downside is that cats with compromised immune systems (FIV or FeLV patients) may suffer from vaccine-induced disease from MLVs.
  • Killed Vaccines: Killed vaccines need a helper to stimulate the natural immune system in the cat, so an adjuvant is added to irritate the immune system, thereby stimulating the creation of antibodies. Some non-adjuvented killed vaccines are now available as well (PureVax). These vaccines attach the killed virus to a completely separate, non-disease causing virus. Because of the risks of infection related to MLVs, it is recommended that immunocompromised cats receive killed vaccines. Two problems arise with killed vaccines: (1) They are not as effective as MLVs and will need to be boostered more frequently and (2) adjuvants cause more inflammation and may play a role in injection site sarcoma formation.

The following vaccinations are only recommended in certain instances by the AAFP:

  • Chlamydiosis: Because adverse reactions to the Chlamydia vaccine happen more frequently than adverse reactions to the disease, and because the vaccine does not prevent clinical infection, but just from severe symptoms, this vaccine is not routinely recommended. Households with multiple cats, catteries, or other environments where infections associated with Chlamydiosis or Conjunctivitis have been confirmed, may consider this vaccine after consultation with a veterinarian. If deemed appropriate, annual revaccination is recommended.
  • Feline Infectious Peritonitis (FIP): Feline Infectious Peritonitis is a dreaded disease, however not all cats who are exposed to it will be infected.The use of the FIP vaccine has been controversial. The AAFP Guidelines indicate that as they currently lack sufficient proof that the vaccine induces clinically relevant protection, its use is not recommended.
  • Bordetella: More commonly found in dogs, Bordetella (kennel cough) is found in shelters and other multiple-cat environments. The usefulness of this vaccine in most cases is minimal, and it is not recommended for routine use, although exceptions may be made for multiple-cat environments.
orange tabby kitten on gray surface
orange tabby kitten on gray surface

Other Vaccination Exceptions

  • Sick cats, cats with chronic disease, such as hyperthyroidism, asthma, chronic renal failure, and/or weakened immune systems should probably not be vaccinated.
  • Consult with your veterinarian before vaccinating a cat receiving steroid therapy.
  • Vaccinations are not recommended for kittens under six weeks, except in extreme situations (orphaned kittens, or kittens in a high-risk environment.)
  • The safety of vaccination in pregnant queens has not been completely evaluated. It is usually not recommended to vaccinate a pregnant queen unless they are at very high risk for contracting disease. If a pregnant cat does need to be vaccinated, modified-live viruses should not be used as they can cause problems with the brain development of the kittens.

FeLV Vaccine

FeLV is a very serious, and always fatal disease, however it does require direct contact with an infected animal to be contracted. The disease is transmitted through saliva and nasal secretions, by biting, sharing food dishes, and other close contact. All cats should be tested for this disease at least once during their lives, and at any other time when they might have had contact with an infected cat or are acting sick. New cats to a household must always be tested prior to introduction to the environment. All cats with a positive ELISA screening test should be segregated from other cats.

It is recommended that all kittens be vaccinated for FeLV so that they have some protection if they ever come into contact with an infected cat. After the initial kitten vaccinations, only cats that spend time outdoors or are otherwise deemed at risk need to receive boosters. In those cases, it should be given every 1-2 years, according to the AAFP guidelines.

black and white cat in tilt shift lens
black and white cat in tilt shift lens

Because of the risk of injection site sarcomas, special vaccination site guidelines have been issued for all recommended vaccines:

  • Rabies: In the right rear leg below the knee
  • FeLV: Left rear leg below the knee
  • Panleukopenia, feline herpesvirus I, feline calicivirus (or 3-way): Right front leg below the elbow.

The reasoning behind this, unpleasant as it may sound, is that a injection site sarcoma on the leg can be treated by amputation, allowing affected cats to survive. Cats are wonderfully adaptive and usually adjust quite quickly to navigating on three legs.

black and white cat on white textile
black and white cat on white textile
gray tabby cat
gray tabby cat
white cat
white cat

Multivalent Cat Vaccines

Traditionally, kittens have been given a 3-way vaccine, which contains agents against feline calicivirus, herpesvirus and feline panleukopenia (FRCP), all given in one shot. These are considered core vaccines and are essential for all cats. A 4-way vaccine, adding Chlamydia is also available, for cats at risk of contracting the latter (primarily show cats.)

Since each needle stick puts a cat at risk for injection site sarcomas, it is generally recommended by veterinarians to use a multivalent vaccine in most cases rather than vaccinating separately.

Cat Vaccine Decision Time

Before making any decision regarding the withholding of recommended vaccinations, it is suggested you do your homework. Don't use this article or any other single article as the basis for a decision, but read as many varying opinions as you can find. This article is not intended to definitively answer any questions, but to stimulate the reader into doing his or her own research. There is much more to be learned about vaccination pros and cons and I have only touched the tip of the iceberg.

The bottom line, as always, is that these are issues you should discuss with your own veterinarian in deciding which vaccinations your cat needs and how often. Every household varies, and the decision is a very personal one, to be made in an informed manner rather than as a result of rumors and panic. In any case, if you and your veterinarian agree to forgo the annual vaccination scheme, make sure you still take your cat in at least once a year for a well-cat check-up and for needed dental cleaning, along with titer-checking, if that's in the plan.