Efficacy of Inactivated AI H5 Vaccines in SPF Chicks Against Challenge with Egyptian H5N8 clade 2.3.4.4b Viruses Isolated in 2017 and 2018

Abstract

We designed an experiment using three commercial inactivated AI H5 vaccines (H5N1, H5N2 and H5N3) in the central laboratory for evaluation of veterinary biologicals (CLEVB) for evaluation of the efficacy of such vaccines against challenge using Egyptian HPAI H5N8 2017 and 2018 official challenge viruses after immunization of SPF chicks with the different AI vaccines. Protection rates in the various groups, induced antibody titers, shedding reduction and histopathological examination of tissues were recorded. Results of the study revealed the following: Protective percentages were as follow: • When challenged with 2017 and 2018 H5N8 isolates, H5N1-vaccinated groups displayed 85% and 0% protection, respectively, when challenged at two WPV and 100% and 92% protec¬tion, respectively, when challenged at three WPV. • H5N2-vaccinated groups displayed 92% and 0% protection, respectively, when challenged at two WPV and 92% and 70% protection when challenged at three WPV. • H5N3-vaccinated groups displayed 100% and 0% protection, respectively, when challenged at two WPV and 100% and 92% protection, respectively, when challenged at three WPV. • There was no evidence of either morbidity or mortality in control negative groups. • When challenged with 2017 and 2018 H5N8 isolates, positive controls displayed 40% and 0% protection, respectively, when challenged at two WPV and 50% and 0% protection, respectively, when challenged at three WPV.