FIG 1.

Influenza vaccine-induced serological Ab response varies with vaccine history. (A) Percentage of peripheral blood CD19⁺ B cells at day 7 after vaccination that were CD27^hi CD38^hi plasmablasts as determined by flow cytometry. The left panel compares the percentage of plasmablasts of all donors vaccinated between the 2010-2011 and 2013-2014 influenza vaccine seasons who had or had not been vaccinated the year prior. The right panel compares the plasmablast response to the 2010-2011 vaccine only. (B) The serum antibody EC₅₀ to the three virus strains present in the 2010-2011 vaccine was determined on the day of vaccination (day 0) with the 2010-2011 TIV and at day 14/21 by ELISA. Each dot represents the fold change increase in the binding EC₅₀ to each strain between day 0 and day 14/21 in an individual donor. Donors are divided according which vaccine(s) they received the year prior (2009-2010 season). The line represents the median fold change within each vaccine group. (C) Fold change in serum Ab EC₅₀ between day 0 and day 14/21 in five individuals to the vaccinating H1N1, H3N2, or influenza B virus strain in the indicated year. Each line represents the yearly serological response to the vaccinating influenza strain of a given donor. None of the donors received the 2009-2010 TIV, while four of them (except 007) received the A/Cal monovalent vaccine. (D) Fold change in serum Ab EC₅₀ as described for panel C to the vaccinating H1N1, H3N2, or influenza B virus strain. As in the data shown in panel C, all 2010-2011 donors had received the A/Cal monovalent vaccine but not the 2009-2010 TIV. After the 2010-2011 season all donors had been vaccinated the year prior as well. Each dot represents the fold increase in serum Abs in each donor with the median indicated by the line. All serum Ab EC₅₀ data are the average from three independent experiments. Statistical analysis was determined using a Mann-Whitney test. Vacc, vaccine; Yam, Yamagata lineage; Vic, Victoria lineage; n.s., not significant.