Figure. Neutralizing antibody titers to subtype H1 swine influenza viruses of the classical swine, North American triple reassortant, and Eurasian avian-like swine lineages in baseline (prepandemic [pre]) and convalescent-phase (postpandemic [post]) serum samples from 28 persons who seroconverted to pandemic (H1N1) 2009 infection, Hong Kong. Complete details on the serologic study cohort from which this subset is drawn are from (4). The pandemic A/California/4/2009 (H1N1) and seasonal influenza A/HK/400599/2008 (H1N1) viruses were used as controls. Orange lines indicate geometric mean titer; green error bars indicate 95% confidence intervals. *p<0.05; †p<0.01.