Companion Animals

Cat Vaccine-Associated Sarcoma Welfare

Injection site sarcoma associated with certain vaccines requires modified vaccination protocols and site monitoring to detect tumours early when treatment is most effective.

Key Facts

ISS occurs at approximately 1 in 10,000-30,000 injection sites in cats
The tumour develops weeks to years after injection and is locally aggressive
Vaccination site should be monitored monthly - any lump persisting 3 weeks requires biopsy
WSAVA guidelines recommend specific injection sites (dorsal neck no longer recommended) to enable adequate surgical margins
Adjuvanted vaccines carry higher sarcoma risk than non-adjuvanted formulations in some studies

Welfare Considerations

Vaccine-associated sarcoma prevention requires modified injection protocols and consistent site monitoring. Early detection enables surgical treatment with adequate margins that achieves the best welfare outcomes.

What You Can Do

Follow WSAVA-recommended vaccination sites to enable adequate surgical margins if sarcoma develops
Monitor all vaccine sites monthly and seek biopsy for any lump persisting more than 3 weeks
Ask your vet about non-adjuvanted vaccine formulations where available for your cat