Quote Originally Posted by smokey the elder View Post
A cat doesn't test positive for FLV if he's had the shots.
My understanding is that waaaay back when the FELV vax first came out they would show positive when they were simply vaccinated, but that is no longer the case.

No vaccine (human or animal) is 100% effective, but to be labled as a vaccine I believe they have to show a 90% or higher effectiveness against the disease when challenged with it. Despite vaccines not being 100% fullproof, they are the best protection available and are definately worth it.

Where I work cats with unknown histories (strays etc) are tested for FELV/FIV and then re-tested 6-8 weeks later to verify the results (regardless if negative or positive). The purpose of the retest on a negative or new cat is that it takes a while for the diseas to show up on a test after they are exposed. An immediate test wouldn't necessarily show if they've contracted the disease yet or not but would show if they've previously contracted the disease, hence the re-tests.

I've never heard of a false negative ever, we only see a very rare false positive, I mean like 1 every other year or two.