Table 3.
Serum Hemagglutination Inhibition and Microneutralization Assay Responses Before and After Each Dose of the 2009 H1N1 Influenza Vaccine
| Hemagglutination inhibition assay |
Microneutralization assay |
|||
| Immunogenicity end point | 25-μg vaccine dose | 49-μg vaccine dose | 25-μg vaccine dose | 49-μg vaccine dose |
| Titer ≥1:40, % (95% CI) | ||||
| Baseline | 7 (2–18) | 7 (2–17) | 13 (5–24) | 16 (7–27) |
| 21 Days after dose 1 | 93 (82–98) | 97 (88–100) | 96 (87–100) | 97 (88–100) |
| 21 Days after dose 2 | 95 (82–99) | 92 (81–98) | 100 (91–100) | 100 (93–100) |
| Delivery | ||||
| Maternal | 85 (71–94) | 62 (46–75)1 | 95 (83–99) | 87 (74–95) |
| Cord blood | 87 (73–96) | 89 (76–96) | 92 (79–98) | 91 (79–98) |
| Seroconversion, % (95% CI) | ||||
| 21 Days after dose 1 | 89 (78–96) | 97 (88–100) | 93 (82–98) | 97 (88–100) |
| 21 Days after dose 2 | 95 (82–99) | 92 (81–98) | 97 (86–100) | 100 (93–100) |
| Geometric mean titer (95% CI) | ||||
| Baseline | 6.8 (5.3–8.7) | 6.3 (5.1–7.8) | 9.5 (7.3–12.4) | 9.6 (7.5–12.3) |
| 21 Days after dose 1 | 384.2 (259.6–568.6) | 460.7 (325.2–652.7) | 444.1 (309.7–636.7) | 595.7 (443.5–800.2) |
| 21 Days after dose 2 | 360.3 (225.0–577.0) | 347.2 (233.3–516.6) | 509.5 (349.6–742.6) | 543.7 (413.1–715.5) |
| Delivery | ||||
| Cord blood | 230.3 (152.1–348.7) | 150.3 (100.9–223.9)2 | 503.5 (329.6–769.1) | 299.3 (197.7–453.2) |
| Maternal | 132.1 (83.0–210.3) | 50.9 (30.5–84.9)1 | 333.8 (216.5–514.6) | 191.0 (121.3–300.6) |
| Geometric mean ratio of cord blood:maternal delivery titer (range) | 1.81 (1.48–2.21) | 2.96 (2.16–4.06) | 1.52 (1.24–1.86) | 1.60 (1.30–1.98) |
NOTE. The number of specimens tested by the hemagglutination inhibition assay for the 25-μg dose group included 55 specimens obtained at baseline and after dose 1, 38 specimens obtained after dose 2, 41 maternal delivery specimens, and 39 cord blood specimens. For the 49-μg dose group, the number of specimens included 58 specimens obtained at baseline and after dose 1, 51 specimens obtained after dose 2, 47 maternal delivery specimens, and 46 cord blood specimens. The number of specimens tested by the microneutralization assay for the 25-μg dose group included 55 specimens obtained at baseline and after dose one, 38 specimens obtained after dose 2, 41 maternal delivery specimens, and 39 cord blood specimens. For the 49-μg dose group, the number of specimens included 58 specimens obtained at baseline and after dose 1, 51 specimens obtained after dose 2, 47 maternal delivery specimens, and 45 cord blood specimens. CI, confidence interval.
P ≤ .02 for comparison of 25-μg dose group with 49-μg dose group.
P = .002 for comparison of cord blood geometric mean titer and maternal delivery geometric mean titer.