Since FIV-vaccinated cats produce antibodies against FIV, distinguishing them from FIV-infected cats is difficult by serological diagnostic methods using FIV and FIV-derived substances. The present invention enables tests for determining the presence or absence of a FIV vaccination history in a cat by detecting antibodies that are produced as a result of vaccination of a cat with an FIV vaccine, but not as a result of FIV infection. Using the methods of the present invention, whether an anti-FIV antibody-positive cat is infected with FIV or has been vaccinated can be conveniently distinguished.
