The use of vaccines in cats provides an essential first defense in the prevention of various diseases. Until recently, a standard set of vaccines was administered to all cats—first as kittens and then annually for life. However, recent studies and experiences have shown that not all vaccines are created equal, and for some cats, the risks may outweigh the benefits of vaccination.
Vaccinating your cat is one of the most important steps you can take to prevent disease and illness throughout their life. Although several major veterinary associations have developed vaccine administration recommendations for cats, there is currently no universally accepted protocol for proper vaccination. As such, it is often up to the veterinarian and the cat owner to determine the best protocol for their individual cat’s needs.
Vaccines fall into two groups: “core” vaccines are those recommended for most cats and include Feline Rhinotracheitis, Calici, Panleukopenia, and Rabies. Non-core, or ancillary, vaccines are those that should only be given to some cats, depending on their risk factors and health status. These include vaccines for Feline Leukemia and Feline Immunodeficiency Virus.
Feline Rhinotracheitis and Calicivirus are two upper respiratory diseases caused by the herpesvirus and calicivirus, respectively. Both are highly contagious between cats and can be transmitted through nose-to-nose contact or by sharing bowls. Although these viruses do not typically cause serious illness in most cats, they can be deadly in kittens and, in some cases, can lead to chronic conditions. Infected cats often sneeze excessively, have a runny nose, and may experience eye discharge. Cats that develop the chronic form of the disease will continue to shed the virus throughout their lives, perpetually able to infect other cats. While vaccination does not provide complete prevention, vaccinated cats may still contract the virus; however, their illness will be less severe, and they will recover more quickly than unvaccinated cats. Vaccination should begin at 6–8 weeks of age, continuing every 3–4 weeks until the cat is 16 weeks old, with a booster given one year later. After that, vaccination should be administered once every three years. The vaccine for Feline Rhinotracheitis and Calicivirus is typically combined with the vaccine for Feline Panleukopenia in the form of the FVRCP vaccine.
Feline Panleukopenia, also known as feline distemper, is caused by the Parvovirus. This highly infectious disease is especially concerning in shelters and boarding facilities, where it can remain active in the environment for months to years. Panleukopenia is particularly dangerous for kittens, causing symptoms such as fever, vomiting, diarrhea, and potentially death. The vaccine for Panleukopenia is generally included with the vaccines for Rhinotracheitis and Calici, administered simultaneously.
Rabies is a disease that can infect any mammal, but cats are particularly at risk due to their tendency to hunt small animals, like mice, rats, and possums, that frequently harbor the infection. Once infected with rabies, the disease is always fatal. Due to the severity of this disease, it is recommended (and in some states, required) that all cats be vaccinated for rabies, regardless of whether they are indoor or outdoor cats. The rabies vaccine should first be administered to kittens at 16 weeks, followed by a booster one year later. After that, a booster vaccination every three years is recommended for optimal protection.
Your veterinarian may recommend a vaccine for the Feline Leukemia Virus if your cat is determined to be at risk for Feline Leukemia (FeLV). FeLV is a retrovirus that attacks the immune system of affected cats and can lead to various secondary diseases, including respiratory infections, weight loss, lethargy, anemia, cancer, and death. FeLV is highly contagious and can be transmitted through saliva and nasal discharge, as well as from an infected mother cat to her kittens. Cats must be tested for FeLV (a simple blood test) before vaccination to ensure they are not already carriers of the disease. Vaccination for FeLV can have side effects, the most serious being a vaccine-associated sarcoma, or cancerous mass, that can form at the injection site. For this reason, it is recommended that the vaccine not be given to indoor-only cats that test negative for FeLV and do not have an opportunity to contact infected cats. In outdoor cats, the risk of contracting FeLV is a far greater threat to their health than the potential for a vaccine reaction, making the vaccine advisable. Kittens should receive their first vaccination at 12–16 weeks of age, followed by a repeat 3–4 weeks later, and then annually thereafter.
Other vaccinations your veterinarian may recommend include those for Feline Immunodeficiency Virus (FIV, a form of feline AIDS), Giardia (an intestinal parasite), and Chlamydiosis (a respiratory infection).
The benefits of vaccines should always be weighed against the risks of potential side effects. Vaccine reactions can occur in any cat and can range from mild transient pain at the injection site or lethargy to more severe reactions. In rare cases, vaccine reactions can lead to vomiting, diarrhea, facial swelling, and even severe shock. These reactions can be life-threatening, and a veterinarian must see the cat immediately. If your cat has a reaction to a particular vaccine, your veterinarian may choose not to administer that vaccine in the future or may provide an alternative under medical observation to ensure another reaction does not occur.
The most severe form of vaccine reaction is a vaccine-associated sarcoma, which starts at the injection site and can spread to surrounding tissue, muscle, and bone. Although this is a potential side effect of any vaccination, it is most commonly associated with the FeLV and Rabies vaccines. To mitigate the potential severity of vaccine sarcomas (which may require surgical removal, radiation, or chemotherapy), these vaccines are administered in the lower hind legs of the cat to facilitate tumor removal if necessary. While vaccine sarcomas are a rare but possible side effect, in most cases, the risk of contracting disease far outweighs the risk of developing a vaccine sarcoma or experiencing other potential side effects.
Your veterinarian can help tailor a vaccination protocol that meets the needs of your cat while minimizing risks and ensuring a long, healthy life for your feline friend.
Vaccine reactions can vary in severity. Mild lethargy and injection site soreness are not uncommon. Immediate allergic reactions can also occur, resulting in symptoms like vomiting, diarrhea, facial swelling, and other signs of shock that must be treated immediately by a veterinarian. Although vaccine reactions can be alarming for owners, they are rarely serious or life-threatening, aside from the potential for vaccine-induced sarcomas. In almost all instances, the benefits of vaccination far outweigh the risks of any adverse reactions.
