Some cats test positive on the coronavirus titer test, some do not.
Those which have never been exposed to ANY form of coronavirus are
called “seronegative.” Those which have been exposed to some form of
coronavirus are called “seropositive.” The Winn Foundation-sponsored
research felt the
Cornell study was flawed because it used cats which had already been
exposed to some form of coronavirus (were “seropositive”) and then
attempted to test the vaccine.
This is not to be confused with the terms “FIP negative” and “FIP
positive” which are used by many labs to indicate that the
coronavirus titer is less than (negative) or more than (positive)
some predefined threshold level.