Broadly, a vaccine is a modified version of a disease-causing organism intended to stimulate the body’s natural immune system to reduce the risk and/or severity of disease in the future. Most often, vaccines guard against viruses, which cannot be cured by any medications currently available, such as feline panleukopenia virus (FPV). Vaccines can also be given against some bacterial diseases, such as bordetella (Kennel Cough).
These bacterial or viral organisms are either inactivated, killed, or broken into smaller parts, then injected under the skin (or intranasally in the case of Kennel Cough). Ideally, the immune system then mounts a mild response, “learning” over 2-4 weeks to recognize the virus or bacterium as foreign and dangerous. Later responses will therefore be much quicker and stronger. If given on an appropriate schedule, some vaccines may fully prevent disease. In other cases, reduction in the frequency and/or severity of disease may be the best result achieved.
Vaccines Do Not Treat Disease
It is important to remember that vaccination is a preventative measure, and cannot be used as treatment once disease has developed in cats. For example, vaccination will not benefit a cat after developing opportunistic infections due to destruction of immune cell precursors by feline panleukopenia infection.
Core vs. Non-core Vaccines in Cats
Vaccines are considered by international veterinary panel recommendations as core, meaning that vaccination of all animals is justifiable, or non-core, meaning that vaccination should only be performed under certain circumstances. Core vaccines are typically life-threatening diseases for which no cure exists, and may represent risk to humans if not controlled (ie. rabies). In cats, rabies, feline herpes virus-1 (FHV1), calicivirus (FCV), and panleukopenia virus (FPV) are considered core vaccinations. The latter three are usually given in combination (“FVRCP”). All other vaccines are considered non-core and should be given only after discussion with your veterinarian about your pet’s risk of developing disease.
Feline non-core vaccines include leukemia virus (FeLV), feline immunodeficiency virus (FIV), and Bordetella. Vaccination against FeLV will make later FeLV tests positive, so should only be performed AFTER an FeLV test is found to be negative in adult cats or those with unknown vaccination history. Vaccination against FIV invalidates routine testing, and is only recommended in cats with a very high risk of exposure, and only after a negative test. Cats receiving this vaccine should be permanently labeled (i.e. microchipped) to avoid future confusion and possible euthanasia if found by others once lost. Bordetella in cats is similar to dogs. Vaccination is not generally recommended against feline infectious peritonitis (FIP) due to limited effectiveness. Vaccination against Giardia is not generally recommended in cats due to a lack of scientific study.
When to Start Vaccinating Cats
Cats receive their initial immunity through their mother’s milk, which contains molecules directed against diseases she encountered or was vaccinated against. These molecules are called “maternal antibodies”, and are responsible for recognizing infectious organisms and alerting the kitten’s immune system to mount a response. Maternal antibodies persist in the blood for up to 16 weeks, but as little as 6 weeks. This is why many vaccines are given at 3-4 week intervals starting at week 6, and ending at 16, weeks of age. It is also why the rabies vaccine is not considered effective by law unless given after 16 weeks of age. Delaying vaccination of your kitten beyond 8 weeks may leave them vulnerable to life-threatening illness. Some vaccines require a booster to be given 3-4 weeks after initial vaccination.
When to Re-vaccinate Cats
Although manufacturers recommend that most re-vaccinations be performed every year, scientific studies have, in some cases, demonstrated effectiveness up to 5 (or even 7) years after administration. Additionally it is important to remember that vaccination, like any medical procedure, involves some risk. For these reasons, many authorities recommend re-vaccination every 3 or more years for rabies, FVRCP, and most non-core vaccines. Bordetella is an important exception, and is effective for up to 6 months if given intranasally (preferred route) or up to a year if injected under the skin (less effective route unless following intranasal).
When Not to Vaccinate Cats
Vaccinations should never be administered to your pet if he or she is sick, immunocompromised, receiving immunosuppressive medications, or has an ongoing infection. This may block the effectiveness of the vaccine, lead to more serious side effects, and/or worsen the current problem. Additionally, the number of vaccines administered should be limited wherever possible to avoid overstimulation of the immune system. A physical examination should be performed by a veterinarian prior to any vaccination. Your pet’s age, lifestyle, and state of health as well as government legislation are key factors that must be discussed with your veterinarian to determine the most appropriate vaccination schedule for your pet.
This article is only a summary and significant variation exists depending upon location and other factors. For specific recommendations about individual vaccinations, please visit the following links.