Further evidence of antigenic drift and protective efficacy afforded by a recombinant HVT-H5 vaccine against challenge with two antigenically divergent Egyptian clade 2.2.1 HPAI H5N1 strains., Rauw, Fabienne, Palya V, Van Borm Steven, Welby S, Tatar-Kis T, Gardin Y, K Dorsey Moore, Aly M M., Hassan M K., Soliman M A., et al. , Vaccine, 2011 Mar 21, Volume 29, Issue 14, p.2590-600, (2011)