TABLE 3.

Hemagglutinin inhibition 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	5.6 (4.9–6.5)	6.1 (5.4–6.8)	5.8 (5.2–6.5)	5.7 (5.0–6.4)	5.3 (5.0–5.5)
Day 21	18.2 (13.5–24.6)	27.5 (18.3–41.1)	45.6 (31.6–65.9)	59.1 (39.4–88.7)	81.7 (58.3–114.5)
Day 42	32.5 (24.6–42.9)	40.2 (27.8–57.9)	62.7 (44.4–88.5)	71.7 (51.0–100.9)	104.3 (77.5–140.3)
Day 180	14.6 (11.7–18.2)	22.3 (15.3–32.4)	24.2 (17.9–32.7)	33.1 (25.3–43.2)	41.5 (32.0–53.7)
Seroprotection (no./total no. [%; 95% CI])a
Baseline	1/56 (1.8; 0.0–9.6)	1/54 (1.9; 0.0–9.9)	1/54 (1.9; 0.0–9.9)	1/55 (1.8; 0.0–9.7)	0/54 (0.0; 0.0–6.6)
Day 21	17/56 (30.4; 18.8–44.1)	22/54 (40.7; 27.6–55.0)	33/54 (61.1; 46.9–74.1)	35/55 (63.6; 49.6–76.2)	40/54 (74.1; 60.3–85.0)
Day 42	28/52 (53.8; 39.5–67.8)	28/53 (52.8; 38.6–66.7)	39/52 (75.0; 61.1–86.0)	42/53 (79.2; 65.9–89.2)	48/54 (88.9; 77.4–95.8)
Day 180	10/51 (19.6; 9.8–33.1)	17/51 (33.3; 20.8–47.9)	22/51 (43.1; 29.3–57.8)	28/51 (54.9; 40.3–68.9)	31/52 (59.6; 45.1–73.0)
Seroconversion (no./total no. [%; 95% CI])b
Day 21	16/56 (28.6; 17.3–42.2)	21/54 (38.9; 25.9–53.1)	32/54 (59.3; 45.0–72.4)	35/55 (63.6; 49.6–76.2)	40/54 (74.1; 60.3–85.0)
Day 42	27/52 (51.9; 37.6–66.0)	27/53 (50.9; 36.8–64.9)	38/52 (73.1; 59.0–84.4)	41/53 (77.4; 63.8–87.7)	48/54 (88.9; 77.4–95.8)
Day 180	9/51 (17.6; 8.4–30.9)	17/51 (33.3; 20.8–47.9)	21/51 (41.2; 27.6–55.8)	28/51 (54.9; 40.3–68.9)	31/52 (59.6; 45.1–73.0)
GMFR (mean [95% CI])c
Day 21	3.2 (2.4–4.3)	4.5 (3.1–6.6)	7.8 (5.5–11.2)	10.4 (7.0–15.6)	15.5 (11.1–21.7)
Day 42	5.7 (4.3–7.5)	6.6 (4.8–9.1)	10.7 (7.6–15.0)	12.7 (9.1–17.8)	19.8 (14.8–26.6)
Day 180	2.7 (2.2–3.3)	3.9 (2.8–5.4)	4.3 (3.2–5.9)	6.1 (4.7–7.9)	8.1 (6.3–10.3)

^aHemagglutinin inhibition (HI) titer, ≥1:40.

^b≥4-fold titer increase compared to baseline.

^cGeometric mean fold rise (GMFR) compared to baseline.