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Ratios of (A) 3c2.A to 3c3.B, (B) 3c2.A to ancestral (3c and 3c3) viruses, and (C) 3c3.B to ancestral viruses during the 2014–2015 season in the United States and Europe. The blue lines and points show the expected direction (but not magnitude) of the spatial difference in lineage ratios based on (A) clade-specific VEs or (B,C) antigenic differences between clades. Error bars indicate 95% multinomial confidence intervals. Complete clade frequencies are shown in Figure A16.
