Duration of Serologic Response to Three Viral Antigens in Cats 

J Am Vet Med Assoc, Jan. 1, 2004 (Vol. 224;224:61–66 ) 

Douglas E. Mouzin, MS, MBA; Marianne J. Lorenzen, DVM; John D. Haworth, DVM, PhD; Vickie L. King, PhD 

Abstract Objective—To determine whether vaccinated cats either remained seropositive or responded serologically to revaccination against 3 key viral antigens after extended periods since their last vaccination.

Design—Serologic survey.

Animals—272 healthy client-owned cats.

Procedure—Cats were = 2 years old and vaccinated for feline panleukopenia virus (FPV), feline calicivirus (FCV), and feline herpesvirus (FHV). On day 0, cats were revaccinated with a vaccine from the same line of vaccines as they had historically received. Antibody titers were measured in sera collected on day 0 (prevaccination titer) and 5 to 7 days later (postvaccination titer). Cats were considered to have responded serologically if they had a day-0 hemagglutination inhibition titer to FPV = 1:40, serum neutralization (SN) titer to FCV = 1:32, SN titer to FHV = 1:16, or = 4-fold increase in antibody titer after revaccination.

Results—The percentage of cats that had titers at or above the threshold values or responded to revaccination with a = 4-fold increase in titer was 96.7% for FPV, 97.8% for FCV, and 88.2% for FHV.

Conclusions and Clinical Relevance—In most cats, vaccination induced a response that lasted up to and beyond 48 months for all 3 antigens. Although not equivalent to challenge-of-immunity studies as a demonstration of efficacy, results suggest that revaccination with the vaccine used in our study provides adequate protection even when given less frequently than the traditional 1-year interval. The study provides valuable information for clinicians to determine appropriate revaccination intervals. (J Am Vet Med Assoc 2004;224:61–66)

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