In a vaccine-related study of almost 32,000 cats, 73 developed inflammatory reactions after being vaccinated, and two developed vaccine site-associated sarcomas.
Study results also showed that:
- Polyvalent vaccines (vaccines for multiple pathogens contained in a single immunization) caused more reactions that monovalent vaccines (single-pathogen vaccines).
- Adjuvanted vaccines (vaccines with additives to boost immune response) cause more reactions than vaccines without adjuvants.
According to W. Mark Cousins, DVM, DABVP, a cookie-cutter approach to vaccinating cats should be avoided:
“Recognize that each patient has a unique level of risk of exposure to pathogens and that risk levels, even for the same patient, can vary with time. Thus, varying types and levels of protection are needed. Avoid using the same vaccination protocol for all cats. Evaluate each patient as an individual at each visit, and vaccinate accordingly.’
Because this type of tumor can recur very quickly if not handled properly, Dr. Cousins recommends all suspected vaccine site-associated sarcomas be managed as follows:
- Step One: A fine-needle aspiration and cytologic examination should be performed to check for malignancy.
- Step Two: Biopsy should follow step one if markedly abnormal cells suggesting malignancy are discovered.
- Step Three: If biopsy confirms vaccine site-associated sarcoma, obtain surgical margins or refer to a specialist for complete removal of the tumor.
Dr. Cousins also advocates use of the ‘3-2-1’ rule, which is to perform a wedge biopsy on any vaccination-site lump that meets at least one of the following criteria:
- Present in any form three months after vaccination
- Greater than or equal to 2 cm across at presentation
- Present for one month after vaccination and is fast-growing.