The HI antibody titers induced by pCA-Egy-H5 post immunization. W1PV: 1-week post vaccination; W2PV: 2 weeks post vaccination; W3PV: 3 weeks post vaccination; W1PB: 1-week post boost; W2PB: 2 weeks post boost; W1PC: 1-week post challenge; W2PC: 2 weeks post challenge.