Fig 4. Seropositivity over multiple influenza seasons.

Subjects were immunized over 3 consecutive seasons, 2014, 2015, and 2016. Each subject was assessed for seropositive titers to the H1N1 and H3N2 components of the vaccine at day 0 and day 21 immunized were categorized according to their seroprotection status at each of the 6 time points analyzed (i.e., days 0 and 21 in all 3 years). Subjects in each age group that had HAI titers less than 1:40 at all 6 time points were assigned a value of “0”. Subjects with an HAI titer of 1:40 or greater at one of the 6 time points was categorized as a “1”. Subjects with an HAI titer of 1:40 or greater at two of the 6 times was categorized as a “2”, at three of the 6 time points, was categorized as a “3”, at four of the 6 times was categorized as a “4”, at five of the 6 times was categorized as a “5”, and subjects with was greater than 1:40 all 6 times was categorized as a “6”. Pie charts for each of these 7 categories was assessed for each age group against the H1N1 or H3N2 component. The n value for each age group was listed beneath each pie chart.