A canine population’s immune resistance to canine distemper virus (CDV), canine parvovirus (CPV), and infectious hepatitis virus (CAV-1) was evaluated. In this study, a total of 112 sera were analyzed. Animals were considered as vaccinated if, in the last two years, they had re-ceived at least one dose of a vaccine that provides joint protection against CDV, CPV, and CAV-1. Animals that had never received any dose of these vaccines were designated as non-vaccinated. CDV, CPV, and CAV-1 antibodies were detected via a modified solid-phase enzyme-linked im-munosorbent assay (ELISA), which detects IgG antibody levels in sera and provides semi-quantitative results in less than 30 min. In total, 41.1% of the dogs had been vaccinated, and 58.9% of dogs were designated as non-vaccinated. Overall, 90.2%, 92.0%, and 78.6% of the tested dogs had positive results for the presence of IgG antibodies against CPV, CDV, and CAV-1, re-spectively. CPV antibodies were present in 93.5% (43/46) of the vaccinated and 87.9% (58/66) of the non-vaccinated dogs, while CDV antibodies were present in 95.5% (63/66) of the vaccinated and 87.0% (40/46) of the non-vaccinated dogs. Finally, CAV-1 antibodies were present in 84.8% (56/66) of the vaccinated and of 69.6% (32/46) the non-vaccinated dogs.