The median frequency of antigen-specific CD4 + T cells per 106 T cells ( 25th quartile ; 75th quartile ) was 852 ( 482 ; 1477 ) for 1xH5N1-AS , 1147 ( 662 ; 1698 ) for 2xH5N1-AS , 556 ( 343 ; 749 ) for 1x-H5N1 and 673 ( 465 ; 1497 ) for 2xH5N1 .