Fig. 1
Immunogenicity of IIV4 among young and older adults living in Tianjin, China. a Dotplots depicting pre- and post-vaccination strain-specific HAI antibody titers as indicated with each panel representing one vaccine strain. Data points for the young (< 65 y) and old age (≥ 65 y) are separated by a vertical line and seroprotective titer 1:40 is illustrated by a horizonal dotted line. P values of statistical significance between the young and old age groups when observed are also shown. b Dotplots illustrating relationship between chronological age and post-vaccination HAI titers with each panel representing one vaccine strain. The HAI titers were log10 transformed, and the correlation was determined using Spearman's rank correlation test. Significant correlation when observed is indicated by a regression line with r and P value shown at the right upper corner of the corresponding panel