In those without detectable baseline antibodies , immunization induced modest antibody titers [ Group1 HAI , 61 ( 26-144 ) ; Group2 HAI , 46 ( 28-76 ) ] with high AI after one dose at day 21 [ Group1 AI , 8.8 ( 7.3-10 .7 ) ; Group2 AI , 8.9 ( 7.8-10 .1 ) ] .