Does Neoplastic Disease Negatively Affect Serum Antibody Titers Against Core Vaccines in Dogs?

Background/Objectives: Neoplasia currently represents the primary cause of death in companion animals worldwide, with one in four dogs developing a tumor during their lifetime. In this scenario, evaluating the immune status against core vaccine-preventable diseases becomes of primary importance to ensure adequate protection in such clinically fragile patients. This study aimed to assess the presence of protective antibody titers (PATs) against core vaccine antigens—canine parvovirus type 2 (CPV-2), canine distemper virus (CDV), and canine adenovirus type 1 (CAdV-1)—in dogs diagnosed with neoplastic disease prior to receiving any antineoplastic therapy. Methods: A total of 120 client-owned, core-vaccinated dogs with various malignant neoplasms were evaluated using an in-clinic semiquantitative assay (VacciCheck^®). Results: Overall, high rates of seroprotection were maintained across the study population, with PATs detected in 93.3% of dogs for CPV-2, 86.6% for CAdV-1, and 79.2% for CDV. High protection levels were consistently observed across different sex, age, and body size categories. Solid humoral memory was retained across all tumor types, although dogs with hemolymphopoietic malignancies (especially lymphomas) exhibited slightly lower protection rates (91.9% for CPV-2, 83.8% for CAdV-1, and 75.7% for CDV) compared to other histotypes. Time elapsed since last vaccination influenced CDV and CAdV-1 titers, whereas CPV-2 immunity remained remarkably persistent even beyond 3 years post-vaccination. Conclusions: These findings indicate that high seroprotection against core vaccine antigens is maintained in dogs with neoplastic disease prior to antineoplastic therapy, with no clear evidence of major humoral impairment compared to historical healthy reference data, thereby reassuring veterinary clinicians and pet owners that routine core vaccine boosters may not represent an immediate priority in canine cancer patients.