TABLE 4.
Neutralizing antibody responses to H9N2 viruses 3 weeks after each immunization and 6 months after first immunization
| Antibody response | Data by dose group |
||||
|---|---|---|---|---|---|
| 3.75 μg | 7.5 μg | 15 μg | 30 μg | 45 μg | |
| Geometric mean titer (mean [95% CI]) | |||||
| Baseline | 7.2 (5.7–9.1) | 9.0 (6.9–11.7) | 7.5 (6.0–9.4) | 8.8 (6.3–12.1) | 6.2 (5.2–7.4) |
| Day 21 | 57.3 (37.5–87.5) | 129.5 (81.1–206.6) | 142.5 (91.3–222.5) | 233.5 (159.1–342.7) | 272.6 (185.0–401.6) |
| Day 42 | 164.3 (118.8–227.4) | 230.8 (151.3–351.9) | 255.1 (181.0–359.6) | 339.4 (247.7–465.1) | 416.3 (300.2–577.4) |
| Day 180 | 37.4 (25.9–53.9) | 67.0 (42.3–106.2) | 66.1 (46.8–93.5) | 101.5 (72.3–142.4) | 117.0 (82.5–165.8) |
| Seroprotection (MN titer ≥ 1:40) (no./total no. [%; 95% CI]) | |||||
| Baseline | 1/56 (1.8; 0.0–9.6) | 8/54 (14.8; 6.6–27.1) | 4/54 (7.4; 2.1–17.9) | 5/55 (9.1; 3.0–20.0) | 3/54 (5.6; 1.2–15.4) |
| Day 21 | 33/56 (58.9; 45.0–70.1) | 41/54 (75.9; 62.4–86.5) | 45/54 (83.3; 70.7–92.1) | 51/55 (92.7; 82.4–98.0) | 50/54 (92.6; 82.1–97.9) |
| Day 42 | 50/52 (96.2; 86.8–99.5) | 47/53 (88.7; 77.0–95.7) | 50/52 (96.2; 86.8–99.5) | 52/53 (98.1; 89.9–100.0) | 53/54 (98.1; 90.1–100.0) |
| Day 180 | 26/51 (51.0; 36.6–65.2) | 32/51 (62.7; 48.1–75.9) | 37/51 (72.5; 58.3–84.1) | 43/51 (84.3; 71.4–93.0) | 42/52 (80.8; 67.5–90.42) |
| Seroprotection (MN titer ≥ 1:80) (no./total no. [%; 95% CI]) | |||||
| Baseline | 1/56 (1.8; 0.0–9.6) | 4/54 (7.4; 2.1–17.9) | 2/54 (3.7; 0.5–12.7) | 5/55 (9.1; 3.0–20.0) | 1/54 (1.9; 0.0–9.9) |
| Day 21 | 24/56 (42.9; 29.7–56.8) | 34/54 (63.0; 48.7–75.7) | 39/54 (72.2; 58.4–83.5) | 43/55 (78.2; 65.0–88.2) | 48/54 (88.9; 77.4–95.8) |
| Day 42 | 43/52 (82.7; 69.7–91.8) | 44/53 (83.0; 70.2–91.9) | 45/52 (86.5; 74.2–94.4) | 51/53 (96.2; 87.0–99.5) | 51/54 (94.4; 84.6–98.8) |
| Day 180 | 13/51 (25.5; 14.3–39.6) | 24/51 (47.1; 32.9–61.5) | 24/51 (47.1; 32.9–61.5) | 33/51 (64.7; 50.1–77.6) | 34/52 (65.4; 50.9–78.0) |
| Seroconversion (no./total no. [%; 95% CI])a | |||||
| Day 21 | 40/56 (71.4; 57.8–82.7) | 44/54 (81.5; 68.6–90.7) | 47/54 (87.0; 75.1–94.6) | 52/55 (94.5; 84.9–98.9) | 53/54 (98.1; 90.1–100.0) |
| Day 42 | 49/52 (94.2; 84.1–98.8) | 49/53 (92.5; 81.8–97.9) | 49/52 (94.2; 84.1–98.8) | 51/53 (96.2; 87.0–99.5) | 53/54 (98.1; 90.1–100.0) |
| Day 180 | 34/51 (66.7; 52.1–79.2) | 41/51 (80.4; 66.9–90.2) | 44/51 (86.3; 73.7–94.3) | 47/51 (92.2; 81.1–97.8) | 52/52 (100.0; 93.2–100.0) |
| GMFR (mean [95% CI])b | |||||
| Day 21 | 8.0 (5.5–11.4) | 14.4 (9.6–21.8) | 18.9 (12.5–28.6) | 26.7 (18.1–39.2) | 44.1 (30.4–63.9) |
| Day 42 | 22.2 (16.3–30.1) | 25.5 (17.4–37.2) | 34.0 (23.7–48.7) | 38.9 (27.2–55.7) | 67.4 (48.4–93.8) |
| Day 180 | 5.4 (4.0–7.4) | 9.1 (6.1–13.5) | 10.3 (7.5–14.0) | 13.3 (9.8–18.0) | 19.9 (14.6–27.1) |
a
≥4-fold titer increase compared to baseline.
b
Geometric mean fold rise (GMFR) compared to baseline.