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. Author manuscript; available in PMC: 2013 Sep 1.
Published in final edited form as: Pediatr Infect Dis J. 2012 Sep;31(9):964–969. doi: 10.1097/INF.0b013e318263280e

Table 2.

Comparison of geometric mean and geometric mean ratio of antibody titers (GMT) before and one month after receipt of trivalent inactivated influenza vaccine (TIV) or placebo in year 1 (2008–2009) and year 2 (2009–2010) in 25 children who received placebo in year 2 (2009–2010).

Group n Pre-dose 1 p-valuea Post-dose 1 p-valuea Pre-dose 2 p-valuea Post-dose 2 p-valuea
Seasonal A(H1N1)b
Geometric mean titer PL-TIVc 16 19 0.32 789 <0.01 77 0.79 174 0.17
PL-PLd 9 37 47 63 69
Proportion titer ≥40 PL-TIVc 16 0.31 0.44 0.94 0.12 0.67 1.00 0.88 0.95
PL-PLd 9 0.56 0.67 0.78 0.78
Proportion titer≥160 PL-TIVc 16 0.25 0.74 0.81 0.01 0.46 0.87 0.75 0.58
PL-PLd 9 0.22 0.22 0.33 0.56
Geometric mean ratio of
post-dose to pre-dose		 PL-TIVc 16 41.2 <0.01 2.3 0.35
PL-PLd 9 1.3 1.1
Proportion ratio ≥4 PL-TIVc 16 0.81 <0.01 0.24 0.80
PL-PLd 9 0.11 0.11
Proportion ratio ≥8 PL-TIVc 16 0.81 <0.01 0.22 0.85
PL-PLd 9 0.11 0.11
Seasonal A(H3N2)b
Geometric mean titer PL-TIVc 16 32 0.20 902 <0.01 177 <0.01 281 <0.01
PL-PLd 9 14 15 15 16
Proportion titer ≥40 PL-TIVc 16 0.56 0.49 1.00 <0.01 0.86 0.03 0.94 0.01
PL-PLd 9 0.33 0.33 0.33 0.33
Proportion titer≥160 PL-TIVc 16 0.25 0.75 0.94 <0.01 0.57 0.02 0.69 0.02
PL-PLd 9 0.11 0.22 0.00 0.11
Geometric mean ratio of
post-dose to pre-dose		 PL-TIVc 16 28.0 <0.01 1.6 0.21
PL-PLd 9 1.1 1.1
Proportion ratio ≥4 PL-TIVc 16 0.88 <0.01 0.20 0.43
PL-PLd 9 0.00 0.00
Proportion ratio ≥8 PL-TIVc 16 0.88 <0.01 0.14 0.69
PL-PLd 9 0.00 0.00
Seasonal Bb
Geometric mean titer PL-TIVc 16 153 0.98 1660 0.03 9 0.51 8 0.62
PL-PLd 9 148 235 7 7
Proportion titer ≥40 PL-TIVc 16 0.88 1.00 0.94 1.00 0.19 0.95 0.19 0.95
PL-PLd 9 0.89 1.00 0.11 0.11
Proportion titer≥160 PL-TIVc 16 0.56 0.69 0.81 1.00 0.00 1.00 0.06 0.77
PL-PLd 9 0.44 0.78 0.00 0.00
Geometric mean ratio of
post-dose to pre-dose		 PL-TIVc 16 10.8 0.00 1.0 0.89
PL-PLd 9 1.6 1.0
Proportion ratio ≥4 PL-TIVc 16 0.69 0.01 0.06 0.77
PL-PLd 9 0.11 0.00
Proportion ratio ≥8 PL-TIVc 16 0.69 0.01 0.06 0.77
PL-PLd 9 0.11 0.00
Pandemic A(H1N1)b
Geometric mean titer PL-TIVc 16 7 0.31 10 0.02 9 0.21 15 0.42
PL-PLd 9 6 7 20 27
Proportion titer ≥40 PL-TIVc 16 0.00 1.00 0.00 1.00 0.14 0.25 0.38 0.65
PL-PLd 9 0.00 0.00 0.44 0.56
Proportion titer≥160 PL-TIVc 16 0.00 1.00 0.00 1.00 0.01 0.27 0.12 0.47
PL-PLd 9 0.00 0.00 0.22 0.33
Geometric mean ratio of
post-dose to pre-dose		 PL-TIVc 16 1.4 0.26 1.7 0.64
PL-PLd 9 1.2 1.4
Proportion ratio ≥4 PL-TIVc 16 0.06 1.00 0.25 0.74
PL-PLd 9 0.00 0.22
Proportion ratio ≥8 PL-TIVc 16 0.00 1.00 0.12 0.95
PL-PLd 9 0.00 0.22
a

P-values comparing between PL-TIV and PL-PL were obtained by the Chi-square test, Fisher’s Exact test, Wilcoxon-signed rank test or Wald test where appropriate.

b

See methods and legend of Table 1 for details of viruses antigens used for hemagglutination inhibition assays.

c

The PL-TIV group consists of subjects who received placebo in 2009–2010 and TIV in 2008–2009. The 2008–09 TIV (year 1) included A/Brisbane/59/2007-like (H1N1), A/Brisbane/10/2007-like (H3N2) and B/Florida/4/2006-like strains.

d

The PL-PL group consists of subjects who received placebo in 2009–2010 and 2008–2009.