TABLE 2

Immunogenicity End Points of the 2009 Pandemic A/H1N1 Influenza Strain Grouped According to GA at Birth and Postnatal Age at Enrollment

Pandemic A/H1N1 StrainPreterm Subjects With GA <32 wk (N = 34)Preterm Subjects With GA 32–36 wk (N = 35)Term Subjects With GA 37–42 wk (N = 32)
Postnatal Age 6–11 mo (n = 17)Postnatal Age 12–23 mo (n = 17)Postnatal Age 6–11 mo (n = 17)Postnatal Age 12–23 mo (n = 18)Postnatal Age 6–11 mo (n = 15)Postnatal Age 12–23 mo (n = 17)
Seroconversion, n (%)
    BaselineNANANANANANA
    28 ± 2 d after dose 116 (94.1)16 (94.1)17 (100.0)18 (100.0)15 (100.0)17 (100.0)
    28 ± 2 d after dose 217 (100.0)17 (100.0)17 (100.0)18 (100.0)15 (100.0)17 (100.0)
GMT (fold increase)
    Baseline9.23 (NA)a98.57 (NA)b99.41 (NA)b74.91 (NA)b73.84 (NA)b95.24 (NA)b
    28 ± 2 d after dose 1366.66 (39.7)a1142.85 (11.6)c1303.52 (13.1)c675 (9.0)c624.61 (8.4)c550.58 (5.8)c
    28 ± 2 d after dose 2821.05 (88.9)a1866 (18.9)1854.11 (18.6)1780 (23.8)1005.71 (13.6)1854.118 (19.5)
Range (SD) of titers
    Baseline5–40 (9.54)5–320 (145.40)5–640 (174.26)5–320 (96.85)5–320 (117.90)5–320 (104.38)
    28 ± 2 d after dose 180–2560 (704.44)a160–5120 (1823.94)80–5120 (1499.92)80–5120 (1534.16)80–2560 (918.44)160–5120 (1748.19)
    28 ± 2 d after dose 280–2560 (766.33)a80–5120 (1546.22)160–5120 (1722.16)160–5120 (1758.76)160–5120 (1119.49)160–5120 (1888.99)
Seroprotection, n (%)
    Baseline0 (0.0)a,b4 (23.5)b11 (64.7)6 (33.3)b5 (33.3)b10 (58.8)b
    28 ± 2 d after dose 116 (94.1)17 (100.0)17 (100.0)18 (100.0)15 (100.0)17 (100.0)
    28 ± 2 d after dose 217 (100.0)17 (100.0)17 (100.0)18 (100.0)15 (100.0)17 (100.0)
  • NA indicates not applicable.

  • a P < .05 versus preterm subjects with a GA of <32 weeks aged 12 to 23 months, preterm subjects with a GA of 32 to 36 weeks aged 6 to 11 months and 12 to 23 months, and term subjects with a GA of 38 to 42 weeks aged 6 to 11 months and 12 to 23 months.

  • b P < .05 versus 28 ± 2 days after dose 1 and versus 28 ± 2 days after dose 2.

  • c P < .05 versus 28 ± 2 days after dose 2.