Although most vaccine manufacturers recommend annual vaccination for feline “distemper” (panleukopenia) and the feline respiratory viruses (calicivirus and feline herpes virus), there is
overwhelming scientific evidence that this is not necessary. The American Association of Feline Practitioners (AAFP) and the World Small Animal Veterinary Association (WSAVA) have issued
specific guidelines regarding this issue. Their recommendations state that, following an appropriate initial vaccination protocol, the FVRCP (distemper/respiratory virus) vaccine need only be given every 3 years at most. The frequency and/or requirements for rabies vaccinations in cats are dictated by local ordinances (see below).
These guidelines were developed as a result of the observation (first reported in 1991) that aggressive soft tissue tumors (sarcomas) seemed to be developing at vaccination sites, particularly at the site of rabies vaccinations. This association was subsequently confirmed and further research showed that all vaccines were implicated. The incidence of tumor formation is estimated to be between 1 in 1000 to 1 in 10,000 per vaccine administered. Although rare, these tumors are extremely aggressive and depending on where they occur, are very difficult and expensive to treat, and carry a poor prognosis. In addition to changing the guidelines for the frequency of vaccination, it is also recommended that all vaccines be given low down on the leg.
Rabies vaccines for cats are required by law in Illinois. Rabies vaccinations are licensed as 1 or 3-year vaccines. The one-year vaccination is required for the first rabies shot, after that we recommend the 3-year vaccine.
Vaccines and Kidney Disease:
A separate issue relating to the vaccination of cats is the possibility that frequent vaccination may increase the incidence of chronic kidney disease. It has been shown that transient inflammation occurs in the kidneys of cats following vaccination. Given the extremely common occurrence of kidney disease in older cats, questions have been raised as to whether the two are related. This has not yet been proven, however, a recent study of factors associated with chronic kidney disease indicated an increased risk of developing kidney disease in cats that were vaccinated frequently as compared to cats not vaccinated frequently.
How effective are the different feline vaccines?
It is important to note that, whereas the rabies and distemper vaccines produce excellent protection against these diseases, the vaccines against the two respiratory viruses (Calicivirus, feline herpes virus) are not 100% effective. Cats still become infected, but the vaccine decreases the severity of the associated clinical signs. Both viruses are harbored for varying periods of time by infected cats.
Calicivirus is usually carried for a few years at most, but feline herpes virus remains in the cat’s nervous system for life. Periods of stress can reactivate this virus many years after the initial infection.
What about the feline leukemia vaccine?
The AAFP and the WSAVA do recommend vaccinating all kittens for feline leukemia (FELV). This recommendation is based on the fact that young cats are much more susceptible to this disease. The
guidelines also recommend continued boosters for indoor/outdoor cats, but they differ on how often these boosters should be given. Dr. Williams has some reservations about the recommendation to routinely vaccinate all kittens against FELV. Although the feline leukemia virus causes a uniformly fatal disease, the incidence of the disease is low (it is currently estimated to be 2% in the general population). A cat contracts the disease either by living in close contact with cats that are positive for FELV or by being bitten by an FELV positive cat. They can also be born with the disease if the mother is infected. When a kitten first presents for vaccination, he or she may have already been exposed, in which case there is no evidence that the vaccination would be of benefit. If the kitten has not been exposed and is not going to be an outdoor cat, Dr. Williams questions the benefit of giving the vaccine.
None of the currently available vaccines are 100% effective and cats develop an innate resistance to infection with this virus with age. One noteworthy exception would be if the kitten or cat was going to live in a household with FELV positive cats. A kitten in such an environment is highly likely to become infected and despite the age related resistance to infection, adult cats living with FELV infected cats can become infected and the longer they are exposed the greater the chances of infection. The recommendation to vaccinate outdoor cats is reasonable as they could potentially be exposed to FELV positive cats, however, in this case they are only likely to contract the disease if they are bitten by a cat carrying the virus.