In subjects who had previously received antigenically matched influenza A ( H5N1 ) pLAIV followed by 1 dose of ISIV compared with those who were naive to influenza A ( H5N1 ) and LAIV and received 2 doses of ISIV , we observed an increased frequency of antibody response ( 82 % vs 50 % , by the hemagglutination inhibition assay ) and a significantly higher antibody titer ( 112 vs 76 ; P = .04 ) .