Table 2. Humoral immunity against pandemic A/H1N1 2009 influenza in vaccinated and non-vaccinated pregnant women at baseline and delivery (n = 678).

	2009 A/H1N1 influenza vaccinated pregnant women N = 256	Non-vaccinated pregnant women N = 422
At inclusion
Geometric mean titer [95% CI]	7.3 [6.7–8.0]	6.7 [6.3–7.1]
Number (%) of women with HI titers >1∶40 [95% CI]	13 (5.1) [2.7–8.5]	19 (4.5) [2.7–7.0]
At delivery
Geometric mean titer [95% CI]	49.8 [43.0–57.7]	7.3 [6.8–7.8]
Number (%) of women with HI titers >1∶40 [95% CI]	179 (69.9) [63.9–75.5]	26 (6.2) [4.1–8.9]
Seroconversion rate§, Number (%) of women [95% CI]	171 (66.8) [60.1–72.5]	10 (2.3) [1.0–4.0]

^§Seroconversion rate is given as the percentage of women with a HI titer <1∶10 at inclusion and a titer of 1∶40 or greater at delivery, or showing a significant increase in antibody titer defined as a titer of 1∶10 or greater at inclusion and at least a fourfold increase in titers between inclusion and delivery.