Table 2.

Serum Hemagglutination Inhibition (HAI) and Neutralizing (Neut) Antibody Responses Before and After Each Dose of Vaccine

	Day 0		Day 28		Day 56		Day 280
Vaccine Group	No. Tested	Before Dose 1	No. Tested	28 Days After Dose 1	No. Tested	28 Days After Dose 2	No. Tested	6 Months After Dose 2
HAI
GMT (95% CI)
Intramuscular H5 HA	114	5.2 (5.0–5.4)	114	11.9 (9.1–15.4)	113	18.1 (13.6–24.1)	112	8.9 (7.3–10.9)
Intradermal H5 HA	113	5.4 (5.0–5.9)	113	13.1 (9.9–17.3)	113	25.2 (18.3–34.5)	111	10.0 (8.1–12.4)
Percentage achieving titer ≥40 (95% CI)
Intramuscular H5 HA	114	0.9 (0–4.8)	114	25.4 (17.7–34.4)	113	35.4 (26.6–45.0)	112	14.3 (8.4–22.2)
Intradermal H5 HA	113	1.8 (.2–6.2)	113	23.0 (15.6–31.9)	113	42.5 (33.2–52.1)	111	18.0 (11.4–26.4)
Percentage achieving ≥4-fold rise (95% CI)
Intramuscular H5 HA	…	NA	114	25.4 (17.7–34.4)	113	35.4 (26.6–45.0)	112	14.3 (8.4–22.2)
Intradermal H5 HA	…	NA	113	22.1 (14.9–30.9)	113	41.6 (32.4–51.2)	111	15.3 (9.2–23.4)
Neut
GMTs (95% CI)
Intramuscular H5 HA	114	5.4 (5.1–5.8)	114	13.3 (10.5–16.7)	113	33.1 (26.5–41.3)	112	11.0 (9.3–13.1)
Intradermal H5 HA	113	5.6 (5.1–6.1)	113	14.3 (11.4–18.0)	113	42.7 (34.3–53.0)	111	13.3 (11.1–16.0)
Percentage achieving titer ≥40 (95% CI)
Intramuscular H5 HA	114	0.9 (0–4.8)	114	21.9 (14.7–30.6)	113	51.3 (41.7–60.8)	112	12.5 (7.0–20.1)
Intradermal H5 HA	113	1.8 (.2–6.2)	113	23.9 (16.4–32.8)	113	60.2 (50.5–69.3)	111	17.1 (10.6–25.4)
Percentage achieving ≥4-fold rise (95% CI)
Intramuscular H5 HA	…	NA	114	21.1 (14.0–29.7)	113	51.3 (41.7–60.8)	112	12.5 (7.0–20.1)
Intradermal H5 HA	…	NA	113	22.1 (14.9–30.9)	113	56.6 (47.0–65.9)	111	15.3 (9.2–23.4)

Abbreviations: CI, confidence interval; GMT, geometric mean titer; HA, hemagglutinin; NA, not applicable.