As expected, IBV antibody was not detected prior to the IBV challenge in the parental FPV vaccinated group and the control group. The H120 vaccine induced the highest level of antibody, and IBV antibody was detected in all chickens by day 7 post-vaccination. The rFPV-IBVS1 vaccinated group induced detectable antibody response by 3 weeks post-vaccination, which is significantly different from the control group (P < 0.05). The level of antibody increased slowly in the rFPV-IBVS1-ChIFNγ-vaccinated group. There was no significant difference between the rFPV-IBVS1-ChIFNγ-vaccinated group and the parental FPV vaccinated group in antibody level (P > 0.05). Following IBV challenge, the level of antibody increased in all groups.