Table 1. Characteristics of the Participants at Enrollment.^*.

Characteristic	mRNA-1273 Booster			Ad26.COV2.S Booster			BNT162b2 Booster
	Primary Ad26.COV2.S	Primary mRNA-1273	Primary BNT162b2	Primary Ad26.COV2.S	Primary mRNA-1273	Primary BNT162b2	Primary Ad26.COV2.S	Primary mRNA-1273	Primary BNT162b2
Group no.	1	2	3	4	5	6	7	8	9
No. of participants	53	51	50	50	49	51	53†	51	50
Sex — no. (%)
Female	26 (49)	32 (63)	29 (58)	27 (54)	16 (33)	23 (45)	29 (55)	26 (51)	23 (46)
Male	27 (51)	19 (37)	21 (42)	23 (46)	33 (67)	28 (55)	24 (45)	25 (49)	27 (54)
Age — yr
Mean	57±14	53±16	55±17	50±14	50±17	50±15	48±14	54±17	50±18
Range	24–81	24–76	22–85	24–77	20–75	20–76	22–74	23–75	19–80
Race and ethnic group — no. (%)‡
Asian	4 (8)	5 (10)	4 (8)	3 (6)	5 (10)	6 (12)	1 (2)	2 (4)	1 (2)
Hawaiian or Pacific Islander	0	0	0	0	0	0	1 (2)	0	0
Black	1 (2)	2 (4)	3 (6)	0	0	2 (4)	0	2 (4)	1 (2)
White	46 (87)	41 (80)	43 (86)	44 (88)	43 (88)	40 (78)	50 (94)	47 (92)	43 (86)
Multiracial	1 (2)	3 (6)	0	3 (6)	1 (2)	2 (4)	1 (2)	0	4 (8)
Hispanic or Latino	4 (8)	4 (8)	3 (6)	2 (4)	0	3 (6)	2 (4)	2 (4)	5 (10)
Other	1 (2)	0	0	0	0	1 (2)	0	0	1 (2)
Ethnic group not reported	0	1 (2)	0	1 (2)	0	0	0	0	0
Interval between first and second primary doses — days
Mean	NA	29±3	23±8	NA	28±3	22±3	NA	28±2	22±5
Range	NA	24–40	16–71	NA	19–36	18–42	NA	24–32	11–46
Interval between second dose and booster — wk§
Mean	14±1	16±2	17±2	18±2	19±4	21±6	20±2	23±5	24±5
Range	12–16	12–20	12–21	14–21	13–26	12–41	11–23	13–29	14–32

^*Plus–minus values are means ±SD. NA denotes not applicable because these participants received a single dose.

^†Listed in this group is one participant who withdrew from the trial during the day 1 visit and did not receive a booster vaccination.

^‡Race and ethnic group were reported by the participant and were collected as two categories, so percentages in each category do not total 100%.

^§For the participants who received the one-dose Ad26.COV2.S primary vaccine, data are listed for the interval after the single dose.