Can vaccinations give cats cancer?
It is possible that vaccinations can give your cat cancer. Currently, the recommended vaccines for cats are rabies, feline leukemia (FeLV), and feline distemper (FVRCP). All three of these vaccines have been associated with sarcomas (1), the first two being more common than FVRCP. Vaccine-associated sarcomas only develop in a very small number of cats (~1/1000 or fewer (1)). However, the cancer is very aggressive and may reappear after removal. To help prevent the occurrence of vaccine-associated sarcomas a Vaccine-Associated Feline Sarcoma Task Force (VAFSTF) was assembled in 1996 (2). Just prior to the increase in sarcomas, adjuvanted vaccines for cats were approved to prevent the occurrence of the disease caused by a live vaccination (2). Adjuvants are used in vaccines to enhance the body’s resistance to a pathogen, thus enabling the use of non-activated (dead) viruses in the vaccines. Adjuvanted vaccines can also reduce the frequency of vaccinations needed because the body remains resistant for a longer period of time.
Among the recommendations given by the VAFSTF, the best way to prevent vaccine-associated sarcomas is to use non-adjuvanted vaccines (3). These vaccines can be more expensive per shot and the overall cost will be greater since you have to vaccinate your cat yearly, as opposed to adjuvanted vaccines that can maintain resistance for 3 years. If you have more than one cat the price really starts to climb. The reduced price and less frequent veterinary visits may entice some to continue the use of adjuvanted vaccines. Reducing the number of vaccines given to a cat will reduce the incidence of vaccine-associated sarcomas as well. Feline leukemia vaccines are not needed for indoor cats (3), so eliminating these vaccines for indoor cats may be beneficial as well.
To aid in the treatment of vaccine-associated sarcomas, it has been recommended that cats receive injections subcutaneously, instead of in the muscle (3). This will allow fore earlier detection and treatment of the sarcomas once they appear (3). Vaccinations in the leg are also recommended, as opposed to the scruff between the shoulder blades (3). A tumor in the leg may require the removal of the leg, but a tumor between the shoulder blades could easily spread to vital organs.
Unfortunately, despite all the research into vaccine-associated sarcomas the incidence of tumors has not decreased (4). The VAFSTF was disbanded in 2005 and the research into vaccine-associated sarcomas decreased, but the issue remains. Vaccine-associated sarcomas are an important issue for cat owners to understand when vaccinating their cats. Vaccinations remain vital to prevent diseases in cats. Hopefully you are now more informed and can make better vaccine decisions for your furry friends.
1. M. J. Hendrick et al., J Am Vet Med Assoc 205, 1425 (Nov 15, 1994).
2. W. B. Morrison, R. M. Starr, J Am Vet Med Assoc 218, 697 (Mar 1, 2001).
3. M. C. McEntee, R. L. Page, J Vet Intern Med 15, 176 (May-Jun, 2001).
4. B. Wilcock, A. Wilcock, K. Bottoms, Can Vet J 53, 430 (Apr, 2012).