Feline Vaccines

Cats finally have their turn this week as we look at vaccinations. I need to bring up a special concern that guides a lot of the decisions we make about vaccinating cats.

Some time ago, an association was found between vaccines and a very nasty kind of cancerous tumor in cats (fibrosarcoma). It was initially believed that adjuvanted vaccines (particularly rabies and leukemia) were directly causing these tumors in cats. What we’ve learned since then has indicated the following:
-Between 1 in 10,000 and 10 in 10,000 cats will develop a sarcoma
-There is a genetic predisposition for developing fibrosarcomas.
-Adjuvant plays a part in development of fibrosarcomas
-ANY injection can lead to a fibrosarcoma

These factors have led to some major changes in the way we vaccinate cats. It’s important to minimize the number of injections that we give cats. We also try to give non-adjuvanted vaccines whenever possible. Lastly, for vaccines that must still have an adjuvant, the type that is used creates the minimum amount of inflammation possible while still ensuring that the vaccine works.


Just as the canine distemper vaccine contains several pathogens, the vaccine we refer to as ‘feline distemper’ also contains multiple portions. Feline Viral Rhinotracheitis, Calicivirus, and Panleukopenia are the components. It’s generally abbreviated as FVRCP.

FVR = Feline Viral Rhinotracheitis
FVR is a herpes virus. It causes respiratory and eye infections. It’s highly contagious by way of oral, nasal, or ocular discharge/contact. Sneezing, coughing, eye discharge, and nasal discharge are the clinical signs that we look for. Some patients will develop a fever, lethargic behavior, or stop eating. Treatment includes supportive care, and most cats recover without complications. Sometimes, a chronic infection results. Also, any cat that contracts FVR will always have the virus, which can flare up in times of stress or other illness. Think about it like cold sores in people (also caused by a herpes virus). This is a modified live vaccine.

C = Calicivirus
Calicivirus is another respiratory/ocular viral disease. It can also cause lameness/musculoskeletal pain and gastrointestinal disease. It’s a highly contagious disease that commonly causes persistent infections. When cats are affected by Calicivirus, they can have fever, lethargy, lack of appetite, ulcers on the tongue, lips and nose, pneumonia, or leg pain.

P = Panleukopenia
Feline Panleukopenia is the cat’s equivalent of canine parvovirus. In fact, feline panleukopenia mutated and became canine parvovirus. Panleuk attacks rapidly growing cells, especially in the bone marrow and gastrointestinal tract. This disease is often fatal. It’s highly contagious. Treatment is just supportive care – IV fluids, antibiotics, and nutritional support. This is a very, very nasty disease.

Some FVRCP vaccines also include a Chlamydia portion. This is a bacterial disease that causes an eye infection. We don’t see a lot of chlamydia cases at the hospital, so we don’t utilize a vaccine with this component


Rabies virus behaves in cats the same way it does in dogs. We have something of a dilemma in cats with Rabies vaccines, though. The 3-year product has an adjuvant, which we know increases the risk of a sarcoma tumor. However, the safest Rabies vaccine out there (a recombinant vaccine) has to be given yearly – which means more frequent vaccination. It’s believed by most veterinary specialists that vaccinating more frequently with a non-adjuvanted vaccine is the least risky option.

Bordetella / Kennel Cough

Cats can catch the bacterial portion of this disease, which is caused by the Bordetella bronchioseptica bacteria. This is ONLY an intranasal vaccine in cats and contains killed bacteria.


Feline Leukemia is a viral disease easily transmitted by bites, casual contact, shared food dishes/litterpans, or transfer from a mother to kittens in the womb or through her milk. Some cats become sick right away. Others can completely clear the virus from their system. Others will have the virus hide in the body and show up again later as they cause severe disease or cancer. Anemia, immunosuppression, and nervous system disease can all result. The vaccine we use for Leukemia is a recombinant vaccine that doesn’t have an adjuvant.

There are two vaccines available for cats that aren’t used by our practice. One is for feline immunodeficiency virus (FIV). That vaccine often doesn’t work very well, and it causes cats have a false positive FIV test result. The other is for feline infectious peritonitis (FIP). That vaccine doesn’t seem to help much at all (and in some studies caused WORSE disease), so we don’t use it.

Kitten Vaccine Series

Maternal antibodies and an immature immune system can create a situation where a single vaccination may not generate a good immune response in a particular kitten, just as with puppies. Therefore, we initiate a series of vaccines that are administered on a regular schedule. This creates a response in the vast majority of patients that is sufficient to protect that kitten from the diseases it is likely to encounter.

We start the series at 6-9 weeks of age with an FVRCP combo vaccine. We continue the distemper series with a vaccination every 3-4 weeks until the kitten is 16-17 weeks old. We try to schedule these so that the kitten doesn’t get more than 3 FVRCP vaccines in total. I personally try to ensure that kittens don’t get more than 2 vaccines at or after 12 weeks of age.

Rabies is given after 12 weeks of age and before 6 months of age. This vaccine’s administration is determined by laws in the particular state. In Michigan, The very first Rabies vaccine a cat gets is good for 1 year. On the next vaccination, if we use the safer recombinant Rabies vaccine, it will again be good for one year. Some clients elect to use the 3-year vaccine (which I do NOT recommend!).

Bordetella intranasal can be given once a kitten is 12 weeks old. Only a single vaccine is needed to produce adequate immunity. This is recommended for any kitten that is going to go outside or be boarded or groomed.

The Leukemia vaccine used to be recommended only for cats that go outside or have exposure to other cats outside the household. However, the new AAFP guidelines have advised that all kittens get vaccinated for Leukemia as part of their initial series. One year later, if the cats are definitely indoor only/low risk, the vaccine is not continued. If the cats have decided they’re going to be indoor-outdoor or have exposure to other cats, the vaccine can be continued. The Leukemia vaccine’s relative safety, we feel that protecting kittens from this dangerous disease is far more important than the risks from vaccination.

Nearly all kittens are finished with their vaccine series by 16 weeks of age. We need to see cats 1 year after the vaccines are completed. FVRCP is boostered at that time, as is Rabies. Depending on a cat’s exposures and lifestyle, we may booster the Bordetella and Leukemia. The final kitten visit and this 1-year booster are the two most important vaccinations in a kitten’s life. At that point in time, we begin to decide on the frequency of vaccinations by taking into account a pet’s lifestyle, exposure to pathogens, health status, and age. While there is a recommended schedule for cats in general, we make a point to administer only the vaccines that are needed by each individual patient.

With the use of non-adjuvanted and/or recombinant vaccines, we’re able to vaccinate cats with far less risk than previously. The number of sarcoma tumors is being watched closely and studied extensively. The need to protect cats is far more important than the risks of vaccination. We still try to minimize the number of injections (vaccines or medications) a cat gets.

You can read more about Feline Vaccine-Associated Sarcomas here.

Thanks for reading!



Filed under immunology, infectious diseases, preventive care

2 responses to “Feline Vaccines

  1. Lots of nasty kitty diseases out there! Do you recommend the same vaccines for strictly-indoor cats as you do for cats who go outside?

  2. For kittens, I recommend the same set whether they’re indoor or outdoor.

    Rabies should ALWAYS be given to cats, no matter what their indoor/outdoor habits are. Bats are one of the main carriers of Rabies in Michigan. If one gets in the house, the cats are likely to be exposed before anyone else. Furthermore, if a cat ever DOES accidentally get outside and isn’t current on the vaccine, then bites somoene, the cat may lose its life so it can be tested for Rabies. With the vaccine on board, that’s not anywhere near as complicated an issue. I just don’t mess around with Rabies. We have a safe vaccine now, so there’s no reason to avoid using it.

    For adult indoor-only cats, we have to very carefully scrutinize their ‘indoor only’ status. If the cats have ANY contact with other cats, even through the screen, or if they spend any time outdoors unsupervised, that counts as indoor-outdoor in terms of disease risk. So, for those ‘mostly indoor’ cats, I recommend FVRCP, Leukemia, and Rabies.

    For truly indoor-only cats, FVRCP is a debatable vaccine. It’s still considered a core vaccine, but I admit that the risk is low for contracting those things. I vaccinate my own cat every 3 years for FVRCP even though her risk is very low. Again, we have a low-risk vaccine that can be given on an extended interval, so I usually do not avoid it.

    Bordetella is a tough one to decide on. Any cat that is exposed to other cats is technically at risk. I recommend this for cats that board or are outdoors for any length of time.

    The risks may be low for contracting these various diseases, but the penalty is quite high if we have an accident. We weigh possible outcomes against risks. With safe vaccines and sensible vaccination intervals, we can make the benefits outweigh the risks and protect the cat.

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