Research overview: efficacy of feline leukemia virus vaccines

FeLV vaccines are non-core products recommended for cats at risk of exposure, especially kittens and outdoor cats, and their introduction contributed to declining FeLV prevalence. Studies have examined their efficacy against persistent viremia, recognizing that no vaccine is fully protective and that vaccination does not replace testing and exposure avoidance. Successive generations included adjuvanted whole-virus and recombinant canarypox-vectored vaccines. This overview synthesizes the vaccinology literature rather than one source, describing how efficacy is measured against persistent infection, why kittens are prioritized given their heightened susceptibility, and how vaccine type relates to both protection and injection-site sarcoma concerns. It matters because FeLV vaccination, combined with testing, formed a key part of the population-level decline of a once-common, serious feline retroviral disease.