How can I protect my cat from FeLV?

Fighting feline leukemia involves three steps:

Testing
Six years after FeLV was discovered, researchers developed a blood test to determine the presence of the virus. Veterinarians generally test cats for FeLV before vaccinating them. Vaccinating an infected cat will not stop the infection and will give the owner a false sense of security, allowing other cats to be exposed. Testing is especially important if a cat commonly goes outdoors, is frequently sick or lives with more than one cat. The chance of contraction increases with the number of cats.

Vaccinating
The FeLV vaccine provides cats with 80 to 90 percent protection from contracting the disease. The vaccine must be re-applied yearly in order to stay effective.

Isolating
Isolating picks up where testing and vaccinating leave off. To cover the vaccine's protection gap, isolating the cat from unknown cats will to reduce chances of exposure and help the vaccine work as thoroughly as it can.