Evaluation of the protective efficacy of a commercial vaccine against different antigenic groups of H9N2 influenza viruses in chickens

摘要: Despite the long-term vaccination programs implemented in China, H9N2 avian influenza viruses (AIVs) continue to persist chicken populations, even vaccinated flocks. We previously demonstrated that AIV isolated from chickens China also underwent antigenic drift and evolved into distinct groups (C, D E). To understand whether of away vaccine strain partially contributed circulation we evaluated protective efficacy a commercial against different AIV. Challenge experiments using indicated prevented shedding group C viruses, but not those more recent E. Vaccinated chickens, with vaccine-induced HI titers 1:1024, shed virus after being infected A/chicken/Shandong/ZB/2007, representative D. Genetic analysis showed E possessed greater numbers amino acid substitutions hemagglutinin protein compared virus, many which were located sites. Our results persistence might be due incomplete protection, should regularly updated maintain optimal protection. Furthermore, policy needs re-assessed, increased veterinary biosecurity on farms, rather than application alone, prevent control influenza.