Table 3.

Antibody Response during Follow-up among Participants without an Elevated Antibody Level at Trial Entry.^*

Variable	ChAd3-EBO-Z	rVSVΔG-ZEBOV-GP	Placebo	P Value
				ChAd3-EBO-Z vs. Placebo	rVSVΔG-ZEBOV-GP vs. Placebo
At 1 wk
No. of participants	478	477	471
Geometric mean titer (95% CI) — EU/ml	88 (82–95)	83 (76–89)	74 (69–80)	<0.001	0.004
Participants with response (95% CI) — %	3.6 (1.9–5.2)	2.5 (1.1–3.9)	1.5 (0.4–2.6)	0.06	0.36
At 1 mo
No. of participants	476	473	468
Geometric mean titer (95% CI) — EU/ml	621 (565–682)	1000 (910–1099)	75 (69–80)	<0.001	<0.001
001 Participants with response (95% CI) — %	70.8 (66.7–74.9)	83.7 (80.4–87.1)	2.8 (1.3–4.3)	<0.001	<0.001
At 6 mo
No. of participants	473	467	458
Geometric mean titer (95% CI) — EU/ml	574 (532–619)	781 (721–847)	87 (80–94)	<0.001	<0.001
Participants with response (95% CI) — %	71.5 (67.4–75.5)	78.4 (74.6–82.1)	5.7 (3.6–7.8)	<0.001	<0.001
At 12 mo
No. of participants	474	468	458
Geometric mean titer (95% CI) — EU/ml	474 (439–512)	818 (752–889)	90 (83–96)	<0.001	<0.001
Participants with response (95% CI) — %	63.5 (59.2–67.8)	79.5 (75.8–83.1)	6.8 (4.5–9.1)	<0.001	<0.001

^*Response was defined as a log₁₀ titer that was increased by a factor of 4 or more from the baseline value among participants without an elevated antibody level at baseline. The P values for group comparisons of the geometric mean titer were based on the log₁₀ titer values at the specified visit, with the baseline log₁₀ titer as a covariate in analysis of covariance. The P values for the group comparisons of the percentage of participants with a response were based on Fisher’s exact test. CI denotes confidence interval.