Duration of Immunity Reference

In a recent study, (Scott and Geissinger, Feline Practice, Vol. 25 (4), July/August 1997) the authors report virus neutralizing (VN) antibody titers in 15 specific pathogen free (SPF) cats vaccinated as kittens with a parenterally administered inactivated triple vaccine FVRCP, then held in strict isolation for up to 6 years. No booster vaccinations were given and 17 unvaccinated SPF cats were housed in contact with the vaccinated cats.

Feline parvovirus (FPV) (panleukopenia) VN antibody titers in the sera were 1:500 or greater in all vaccinated cats for at least 6 years after vaccination. The mean titer for all vaccinated cats remained at approximately 1:5,000. Titers of 1:8 or greater are considered to be protective for FPV. Mean feline herpesvirus (FHV-1) VN antibody titers of vaccinated cats were 1:18 at 2 months after vaccination, 1:12 at 3 years, 1:9 at 4 years, and 1:4 at 5 years. All titers were positive through year 3. From 4 to 6 years, FHV-1 antibody titers were low to negative, but negative titers were usually followed by low positive titers the next year, indicating a persistence of memory B cells within these vaccinated cats. All vaccinated cats had positive feline calicivirus (FCV) VN antibody titers for 4 years after vaccination, and all but 1 cat had a positive titer at year 5.