Vaccination for FPV is highly effective if performed correctly. A thoughtful and effectively implemented vaccine program can substantially reduce spread of infection in a shelter. Modified live subcutaneous vaccination will provide more rapid protection than killed vaccine, which requires a booster to be effective.
All cats four weeks of age and older should receive a modified live panleukopenia vaccine immediately upon shelter entry. Cats begin mounting an immune response to panleukopenia immediately and develop full immunity in three days.1 A delay of even a few hours renders the vaccine far less useful. Even injured and mildly ill cats should be vaccinated.
For pregnant cats expected to carry kittens to term, balance the risk of inducing abortion or birth defects (reportedly very uncommon with currently available vaccines) against the risk of death of mom and kittens from virulent disease. Additionally, vaccinating the queen for the respiratory viruses contained in the FVRP vaccine can confer some protection to the kittens by generating maternal antibodies. In most cases, the benefits outweigh the risk of vaccination. However, for pregnant cats seized as part of a legal case or cats in a shelter where the risk of panleukopenia is extremely low, a killed vaccine may be preferable.
For more information, refer to Vaccination in Animal Shelters and the American Association of Feline Practitioners Vaccination Guidelines.