Vaccines are important to protect the health of your cat against diseases that can cause severe upper respiratory infections, lethal rabies viral infections, as well as cancer-causing leukemia viruses. Every cat faces different infection risks, depending on their age, health status, lifestyle, and environment. Kittens, with their developing immune systems, are particularly susceptible to viruses. Not only are they exposed to viruses from their mothers in utero and during the neonatal period when they are too young to be vaccinated, they also have left-over antibodies from their mother’s milk that prevent the vaccines from being fully effective until 13 weeks of age. Outdoor cats risk bites and fights with feral cats or wild animals, increasing their exposure risk for rabies, Feline Leukemia virus, and Feline Immunodeficiency Virus. Indoor cats in multicat households can pass around various strains of upper respiratory viruses causing an entire household to become ‘a sneezy, snotty, green booger shedding mess.’

While vaccines are incredibly important to protecting your cat’s health, it is important to know that there are possible side-effects to vaccinating your cat. For the vast majority of cats, after vaccination, a cat may feel some injection site soreness, mild lethargy, or low-grade fever with flu-like symptoms. Though rare, specifically 1 in 10,000 cats, I want to address the possibility of a feline vaccine-associated sarcoma (cancerous tumor) developing. These aggressive tumors are thought to be caused by the adjuvant added to ‘killed viral vaccines’. Adjuvants are substances that promote inflammation at the injection site, and subsequently cause stronger immune responses and antibody level development. From as little as 3 months to as long as 13 years, these adjuvants can cause chronic inflammation, and over time, can lead to the development of tumors at the injection site. As part of routine veterinary monitoring for the development of these tumors and other side-effects, veterinarians vaccinate cats for the different viruses in different legs. This helps us correctly identify the vaccine that has caused the potential side effects- 1) Right front- Feline Viral Rhinotracheitis-Calici-Panleukopenia (FVRCP), 2) Right rear- Feline Rabies Virus, and 3) Left rear- Feline Leukemia Virus.

Historically, Lexington Animal Hospital has used 2 different killed viral vaccines- the killed Feline Rabies vaccine and the killed Feline Leukemia vaccine (part of the Feline Combo vaccine). For the vast majority of cats, these vaccines have not or will not trigger cancer. However just this October, Loki, a sweet 3 year old female cat, developed a vaccine-associated sarcoma from her Rabies vaccine given this past July! Because these tumors are so aggressive, Loki had to have her entire right hind leg amputated. Luckily, subsequent testing has shown that the tumor had not spread to her lymph nodes or lungs, and the surgery has been curative.

After my experience with Loki and her owner, and through discussions with vaccine specialists and cancer specialists, I have become very passionate about no longer using these adjuvant containing vaccines. We have switched our Feline Rabies and Feline Leukemia vaccines from “killed adjuvant containing vaccines” to “adjuvant-free vaccines.” In addition, in accordance with the guidelines from the American Association of Feline Practitioners and the American Animal Hospital Association, we will now be administering the FVRCP vaccine every 3 years and the Feline Leukemia vaccine every 2 years.

At Lexington Animal Hospital, we are passionate about your cat’s health and want to do what we can to ensure a long, happy, active and healthy life. Please feel free to ask me or the staff about these changes and if you have any other questions or concerns about your cat.

Sincerely,

Dr. Meghan Ryan