In this study we investigated whether vaccination with a CPV-2b containing vaccine would inducecross-reactive antibody responses to the other CPV-2 variants. Two studies where dogs were vaccinated with a multivalent vaccine, subsequently challenged with CPV-2b and sera samples analysed are pre-sented. Six week old pups with defined serological status were vaccinated twice, three weeks apart andchallenged either 5 weeks (MDA override study) or one year after vaccination (duration of immunity study). Sera samples were collected before each vaccination and at periods throughout each study.