Haemagglutination inhibition antibody geometric mean titres were 17.6 ( 95 % CI 13.7 to 22.5 ) for 1xH5N1-AS , 18.4 ( 95 % CI 14.2 to 23.8 ) for 2xH5N1-AS , 12.3 ( 95 % CI 8.9 to 16.9 ) for 1xH5N1 and 9.8 ( 95 % CI 6.7 to 14.4 ) for 2xH5N1 .