EXPRESS: Antibody responses to inactivated (adjuvanted) and attenuated (non-adjuvanted) feline panleukopenia virus vaccination, including in different injection sites.

Abstract

OBJECTIVES: Concern about feline injection-site sarcomas (FISSs) has prompted recommendations to vaccinate in the hindlimb or tail instead of the scruff, but evidence of adequate immune response at these sites is limited. This field study evaluated the antibody response to feline panleukopenia virus (FPV) in kittens vaccinated with one of two commercial vaccines, injected at different sites. METHODS: An inactivated (killed) adjuvanted vaccine was injected subcutaneously into the scruff, left distal hindlimb, or proximal tail. A modified-live virus (MLV) was given in the scruff only. Cats were given a booster vaccination in the same site and using the same vaccine type. Kittens were sampled at four timepoints over 12 months (T0, T1, T2, T12). Protective FPV antibody titres were determined by haemagglutination inhibition (HI; negative < 1:32, positive &#x2265; 1:32). RESULTS: Samples from 100 kittens and 77 adults were available for FPV antibody testing. Eight kittens were found to be HI-positive at T0. Protective titres did not differ significantly among the three injection sites for the inactivated vaccine. Antibody titres were higher in kittens given the MLV vaccine compared to kittens given the inactivated vaccine at T1 (p = 0.006) and T12 (p = 0.001). However, the proportion of kittens protected in each group (MLV vaccine vs inactivated vaccine) was the same. A single vaccination was sufficient to produce protective antibody levels in 91% of kittens, irrespective of whether they were given the MLV (scruff) or inactivated vaccine (at any site). CONCLUSIONS AND RELEVANCE: Both inactivated and MLV vaccines induce protective titres against FPV. Comparable FPV antibody responses are elicited when inactivated vaccines are administered into the scruff, left distal hindlimb, or proximal tail. Notably in this study, the MLV vaccine tended to produce higher antibody titres. These results support evidence-based recommendations on vaccination site selection to mitigate FISS risk.