Duration of serologic response to three viral antigens in cats

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.