Fig 7. Vaccine induced back boosting to H3N2 historical viruses.
HAI activity in sera collected from subjects pre- (day 0) and post- (day 21) vaccination were examined for the number of strains in detected with a titer greater than 1:40 against each strain the H3N2 influenza virus panel. Subjects from three consecutive influenza seasons (2014, 2015, 2016), along with the number of subjects per season (n value) are listed on the x-axis at day 0 and 21 post-vaccination. The number of strains recognized by each subject is listed on the y-axis. Panel A-D represent subjects between ages of 18–34 y.o (red symbols). Panel E-H represent subjects between the ages of 35–49 y.o (green symbols). Panel I-L represent subjects between the ages 50–64 y.o. (blue symbols). Panel M-P represent subjects between the ages of 65–85 y.o. (orange symbols). Subjects seronegative (<1:40) to the H3N2 component in the vaccine at day 0 and remained seronegative post-vaccination (Panels A, E, I, M). Subjects seronegative (<1:40) to the H3N2 component in the vaccine at day 0 but seroconverted (four-fold increase in titer with a titer ≥1:40) post-vaccination (Panels B, F, J, N). Subjects seropositive (≥1:40) to the H3N2 component in the vaccine at day 0 but did not seroconvert post-vaccination (Panels C, G, K, O). Subjects seropositive (≥1:40) to the H3N2 component in the vaccine at day 0 and seroconverted (four-fold rise in titer) post-vaccination (Panels D, H, L, P).