In sum, if you know your cats are seronegative, and they are
older than 16
weeks, the vaccine is recommended by both the Cornell Feline Health
Center and the consensus reached at the Winn Foundation sponsored
FIP/FECV seminar. If your cat is already seropositive, there is not
much evidence that the vaccine will help.

The vaccine will be more of
a help when

  • the manufacturers demonstrate its effectiveness
    against the Type I strain of FIP
  • it is shown to be effective in
    seropositive cats, and
  • it could be shown to be safe and effective for
    kittens under the age of 16 weeks.

However, it appears that there is work being done to develop a
FECV vaccine. Preventing FECV infections in the first place, and
thus preventing FECV from mutating into FIP, might turn out to be
another technique in trying to protect against FIP.