In each study the antibody profiles were very similar; serological responses against CPV-2a, CPV-2band CPV-2c were higher than those for CPV-2. Nevertheless, responses against CPV-2 were well above levels considered clinically protective. In each study dogs also showed a rapid increase in antibody titresfollowing vaccination, reached a plateau following second vaccination with a slight decline to challengeafter which rapid anamnestic responses were seen. Evaluation of the serological responses suggestsvaccination with CPV-2b would cross-protect against CPV-2a and CPV-2c, as well as against CPV-2 whichis now extinct in the field.