Figure 3

Antigenic evolution of Vietnamese H5 HPAIVs and antibody titers of field vaccinated poultry antisera. (A) Antigenic cartography of representative Vietnamese H5 HPAIVs. Both vertical and horizontal axes represent antigenic distance. The spacing between gridlines is equivalent to an antigenic unit distance corresponding to a 2-fold HI difference. The dot lines indicate a combination of the homologous viruses and antisera. Vaccine-primed antisera were prepared in laboratory condition. Supplementary Table S6 describes abbreviation and HI titers. (B) Detectable HI titers of 44 vaccinated poultry antisera samples collected in the field against the reference antigen and representative inactivated H5 HPAIVs. The linear black lines indicate the median of antibody levels within each population. The horizontal dot line at 8 HI is the minimum protective level²³.