Healthy adults ( n = 521 ) received 2 vaccine doses ( days 0 and 21 ) of either investigational CC-H5N1 vaccine ( 1.9 g or 3.75 g of hemagglutinin antigen [ HA ] with the AS03 adjuvant system or 15 g of plain HA ) , embryonated-egg-derived vaccines ( 3.75 g of HA with AS03 or 15 g of plain HA ) , or placebo .