Figure 2. . . . . . Percentage of samples with hemagglutination-inhibition titer >32 during consecutive waves of influenza activity, England, summer 2009 and 2009-10 and 2010-11 influenza seasons. Data were plotted from all available results determined by hemagglutination-inhibition assay on samples from all regions. A) Children <5 years old. B) Children 5–14 years old. C) Persons 15–24 years old. D) Persons 25–44 years old. E) Persons 45–64 years old. F) Persons 65–74 years old. G) Persons >75 years old. Black line, results from all regions; gray line, results from the North West and South West regions, which provided samples throughout the entire period. Error bars indicate 95% confidence intervals.