FeLV vaccination is one of the most important welfare-protective interventions for cats with outdoor access or exposure to cats of unknown status.
FeLV vaccination represents a welfare investment that costs little relative to the welfare burden of FeLV infection. A cat who contracts FeLV faces progressive immune compromise, increased susceptibility to infection, anemia, and eventual lymphoma — a welfare trajectory that unfolds over years. The vaccination that prevents this welfare burden is inexpensive, safe, and effective for cats at risk. The decision not to vaccinate outdoor cats with potential exposure to cats of unknown FeLV status is a risk decision that may impose a substantial and entirely preventable welfare burden on the unvaccinated cat.