In a recent study cats were tested in the same manner as in the vaccine manufacturer's tests. At the end of an 8-week period, 30% of cats vaccinated, and 60% of the controls demonstrated FIP-positive conditions from tissue examinations. This demonstrates a 50% "preventable percentage."

Another recent field trial ran for 16 months using 500 cats in a no-kill shelter with endemic FIP. The fact that this is a shelter makes it a different makeup than a cattery (and some multi-cat households) because the average age of a cat was approximately 2 years old, and there were no kittens under 16 weeks old. However ALL cats tested were seronegative prior to exposure in the shelter. During the time of the study, 0.8% of the vaccinated cats died and 3.25% of controls died of FIP. [This is statistically significant at p=.048, which means that there is a 95.2% probability that this result is not random] So, for seronegative cats over the age of 16 weeks, this study shows a 75% efficacy rate. Vaccination after exposure (after a cat is already seropositive) is not helpful in preventing the disease.