ABSTRACT
Traditional live Infectious Bursal Disease virus [1DDV] vaccines were thought to have some v-4 degree of adverse effect on the bursa of fabricous of chickens, which in turn may interfere with antibody production against other poultry vaccines. In this study, 15 broiler flocks vaccinated -; against avian influenza [AI] virus were sampled for serum. The flocks have received IBDV vaccination either from the conventional live vaccines or with the new recombinant subunit vaccine. Haemagglutination inhibition [HI] test was carried on sera using different AI antigens. Sera measured by the variant A/chicken/EgypWRLCU67/2011 [H5N1] isolate showed significant difference [P<0.05] between mean HI titers of bird vaccinated by traditional IBDV. vaccines and titers of those vaccinated with the subunit vaccine. Results indicate that live IBDV vaccines may affect the efficacy of AI vaccine, and the study encourages the use of the field AI isolates for reliable interpretation of HI test results