Table 1.
Antigenic Distances and Results of Correlation Coefficient and Bootstrap Analyses for Influenza H3 Variants Characterized by Human Postvaccination Sera
| H3N2 Virusa | Antigenic Distanceb | H1-Priming vs no H1/B-Priming | B-Priming vs no H1/B-Priming | H1/Bris-Priming vs no H1/B-Priming | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| No H1/B-Primingc | H1-Priming | B-Priming | H1/Bris-Priming | Correlation Coefficientd | Bootstrap Analysise | Correlation Coefficient | Bootstrap Analysis | Correlation Coefficient | Bootstrap Analysis | |||||
| Individual | Average | Individual | Average | Individual | Average | Individual | Average | |||||||
| SWZ/13e (2015–2016 vaccine prototype) | ||||||||||||||
| HK/4801e | 0.86 | 1.14 ± 0.33 | 0.54 | 1.12 ± 0.35 | 0.82 | 1.08 ± 0.27 | 0.40 | 1.00 ± 0.33 | 0.29 | 0.25 ± 0.26f,g | 0.86 | 0.86 ± 0.02f | 0.56 | 0.49 ± 0.19 |
| SWZ/13c | 1.06 | 1.14 | 1.20 | 0.97 | ||||||||||
| MI/15c | 1.80 | 1.08 | 1.62 | 1.19 | ||||||||||
| WI/20c | 1.19 | 1.66 | 1.15 | 1.43 | ||||||||||
| TX/50e (2014–2015 vaccine prototype) | ||||||||||||||
| SWZ/13e | 0.92 | 1.38 ± 0.44 | 1.25 | 1.33 ± 0.63 | 1.04 | 1.44 ± 0.36 | 1.18 | 1.43 ± 0.51 | 0.70 | 0.53 ± 0.27 | 0.95 | 0.91 ± 0.05 | 0.88 | 0.85 ± 0.07 |
| NC/13e | 1.76 | 1.77 | 1.81 | 1.80 | ||||||||||
| TX/50c | 1.37 | 0.88 | 1.53 | 1.46 | ||||||||||
| NC/13c | 2.22 | 2.60 | 2.19 | 2.55 | ||||||||||
| VIC/361e (2012–2013 vaccine prototype) | ||||||||||||||
| TX/50c | 1.42 | 2.02 ± 0.89 | 0.72 | 2.24 ± 1.15 | 1.64 | 1.98 ± 0.84 | 0.81 | 2.22 ± 1.07 | 0.90 | 0.84 ± 0.09g | 0.98 | 0.98 ± 0.01 | 0.90 | 0.87 ± 0.07 |
| DE/15c | 3.26 | 3.25 | 3.29 | 3.33 | ||||||||||
| OH/02c | 3.52 | 4.14 | 3.37 | 3.85 | ||||||||||
| SC/16c | 2.35 | 2.24 | 2.43 | 1.91 | ||||||||||
aThe H3N2 vaccine prototype virus and variants used for the 2015–2016 Northern Hemisphere influenza vaccine trial include: egg-grown A/Switzerland/9715293/2013 (SWZ/13e) and A/Hong Kong/4801/2014 (HK/4801e), and cell-grown SWZ/13c, A/Michigan/15/2014 (MI/15c), and A/Wisconsin/20/2015 (WI/20c). The H3N2 vaccine prototype virus and variants used for the 2014–2015 Northern Hemisphere influenza vaccine trial include: egg-grown A/Texas/50/2012 (TX/50e), SWZ/13e, and A/North Carolina/13/2014 (NC/13e), and cell-grown TX/50c and NC/13c. The H3N2 vaccine prototype virus and variants used for the 2012/13 Northern Hemisphere influenza vaccine trial include egg-grown A/Victoria/361/2011 (VIC/361e) and cell-grown TX/50c, A/Delaware/15/2012 (DE/15c), A/Ohio/02/2012 (OH/02c), and A/South Carolina/16/2012 (SC/16c).
bAntigenic distances of individual H3N2 variants to the vaccine prototype virus were calculated based on the postvaccination hemagglutination inhibition (HAI) titers. Average distances are shown as mean ± standard error of the means (SEM).
cHuman postvaccination sera were selected based on their paired prevaccination HAI titers against the corresponding vaccine strains: (1) No H1/B-priming (prevaccination HAI titer of <40 against H1N1 and B vaccine strains); (2) H1-priming (prevaccination HAI titer of ≥40 against H1N1 but <40 against type B virus); (3) B-priming (prevaccination HAI titer of ≥40 against type B but <40 against H1N1; (4) H1/Bris-priming (prevaccination HAI titer of ≥40 against H1N1 including those with prevaccination HAI titer of ≥40 against B/Brisbane/60/2008 [Bris] vaccine strain). There are 43 no H1/B-priming subjects, 5 H1-priming subjects, 38 B-priming subjects, and 9 H1/Bris-priming subjects identified for the 2015–2016 vaccine trial. There are 18 no H1/B-priming subjects, 3 H1-priming subjects, 30 B-priming subjects, and 13 H1/Bris-priming subjects identified for the 2014–2015 vaccine trial. There are 20 no H1/B-priming subjects, 5 H1-priming subjects, 23 B-priming subjects, and 9 H1/Bris-priming subjects identified for the 2012–2013 vaccine trial.
dCorrelation coefficient values were determined by Pearson product-moment correlation coefficient analysis on the antigenic distances of H3 variants characterized by human postvaccination sera with H1-priming, B-priming, or H1/Bris-priming as compared to those with no H1/B-priming. A correlation coefficient of 1 suggests a perfect positive correlation, –1 indicates a perfect negative correlation, and 0 denotes no correlation.
eBootstrap analyses, which were performed to minimize the potential biases from small sample sizes, randomly selected 100 sub-HAI tables from a corresponding parent table to calculate the correlation coefficient values ± SEMs on the H3 antigenic distances derived.
f P < .05 vs 2015–2016 B-priming group as determined by 2-way analysis of variance (ANOVA).
g P < .05 vs 2012–2013 H1-priming group, as determined by 2-way ANOVA.