TABLE 1.

Participant demographics

Characteristic	Value for:
	10-Day challenge		90-Day challenge
	Vaccine (n = 26)	Placebo (n = 22)	Vaccine (n = 20)	Placebo (n = 16)
Mean age, yr (SD)	31.3 (5.9)	31.6 (7.8)	34.8 (8.1)	30.6 (6.4)
Sex, no. (%)
Male	17 (65.4)	11 (50.0)	14 (70.0)	10 (62.5)
Female	9 (34.6)	11 (50.0)	6 (30.0)	6 (37.5)
Race, no. (%)
Black/African-American	14 (53.9)	13 (59.1)	14 (70.0)	12 (75.0)
White	8 (30.8)	9 (40.9)	6 (30.0)	4 (25.0)
Other	4 (15.3)	0	0	0
Blood group, no. (%)
O	11 (42.3)	12 (54.5)	13 (65.0)	6 (37.5)
Non-O	15 (57.7)	10 (45.5)	7 (35.0)	10 (62.5)