Table 1.
Characteristics of the Participants at Baseline (Modified Intention-to-Treat Population).*
| Characteristic | PrEP Cohort | PLWH Cohort | Total (N =501) | ||
|---|---|---|---|---|---|
| Doxycycline Group (N = 220) |
Standard-Care Group (N = 107) |
Doxycycline Group (N = 119) |
Standard-Care Group (N =55) |
||
| Median age (IQR) —yr | 36 (31–42) | 36 (31–42) | 43 (36–54) | 42 (37–50) | 38 (32–47) |
| Race — no./total no. (%)† | |||||
| White | 144/209 (69) | 66/104 (63) | 74/116 (64) | 37/53 (70) | 321/482 (67) |
| Black | 9/209 (4) | 5/104 (5) | 15/116 (13) | 7/53 (13) | 36/482 (7) |
| Asian or Pacific Islander | 33/209 (16) | 12/104 (12) | 7/116 (6) | 1/53 (2) | 53/482 (11) |
| Multiple races or other | 23/209 (11) | 21/104 (20) | 20/116 (17) | 8/53 (15) | 72/482 (15) |
| Hispanic or Latino ethnic group — no. (%)† | 55 (25) | 41 (38) | 41 (34) | 14 (25) | 151 (30) |
| Gender identity — no. (%) | |||||
| Man | 212 (96) | 107 (100) | 109 (92) | 54 (98) | 482 (96) |
| Transgender woman or gender-diverse | 8 (4) | 0 | 10 (8) | 1 (2) | 19 (4) |
| Gender of sexual partners — no./total no. (%) | |||||
| Men only | 191/220 (87) | 90/107 (84) | 105/118 (89) | 48/55 (87) | 434/500 (87) |
| Multiple genders | 29/220 (13) | 17/107 (16) | 13/118 (11) | 7/55 (13) | 66/500 (13) |
| Annual income— no./total no. (%) | |||||
| <$20,000 | 31/219 (14) | 13/106 (12) | 42/119 (35) | 17/55 (31) | 103/499 (21) |
| $20,001-$50,000 | 64/219 (29) | 39/106 (37) | 40/119 (34) | 22/55 (40) | 165/499 (33) |
| $50,001-$75,000 | 45/219 (21) | 14/106 (13) | 22/119 (18) | 5/55 (9) | 86/499 (17) |
| >$75,000 | 79/219 (36) | 40/106 (38) | 15/119 (13) | 11/55 (20) | 145/499 (29) |
| STI in the past 12 mo — no. (%) | |||||
| Gonorrhea | 155 (70) | 78 (73) | 71 (60) | 39 (71) | 343 (68) |
| Chlamydia | 144 (65) | 63 (59) | 58 (49) | 27 (49) | 292 (58) |
| Syphilis‡ | 32 (15) | 16 (1) | 35 (29) | 17 (31) | 100 (20) |
| Two or more STIs in the past 12 mo — no. (%) | 106 (48) | 44 (41) | 39 (33) | 26 (47) | 215 (43) |
| Any STI at baseline — no./total no. (%) | 65/219 (30) | 27/106 (25) | 34/114 (30) | 20/55 (36) | 146/494 (30) |
| Gonorrhea | 40/218 (18) | 20/107 (19) | 25/117 (21) | 14/54 (26) | 99/496 (20) |
| Chlamydia | 31/219 (14) | 11/107 (10) | 11/117 (9) | 8/54 (15) | 61/497 (12) |
| Syphilis | 5/219 (2) | 1/107 (1) | 11/117 (9) | 4/55 (7) | 21/498 (4) |
| Median no. of sexual partners in the past 3 mo (IQR) | 8 (4–17) | 10 (5–16.5) | 7 (3–18.5) | 10.5 (3–20) | 9 (4–17) |
| Transactional sex during lifetime — no./total no. (%)§ | 47/219 (21) | 28/107 (26) | 47/116 (41) | 21/49 (43) | 143/491 (29) |
| Substance use in the past 3 mo — no./total no. (%) | 112/216 (52) | 66/107 (62) | 77/117 (66) | 38/53 (72) | 293/493 (59) |
| Stimulants: methamphetamine, cocaine, or crack | 51/216 (24) | 22/107 (21) | 50/117 (43) | 23/53 (43) | 146/493 (30) |
| Heroin or other opioids | 2/216 (1) | 1/107 (1) | 9/117 (8) | 2/53 (4) | 14/493 (3) |
| Ecstasy, GHB, or ketamine | 63/216 (29) | 34/107 (32) | 39/117 (33) | 21/53 (40) | 157/493 (32) |
| Amyl nitrates, also known as poppers | 93/216 (43) | 47/107 (44) | 56/117 (48) | 28/53 (53) | 224/493 (45) |
| Marijuana | 96/216 (44) | 56/107 (52) | 60/117 (51) | 27/53 (51) | 239/493 (48) |
The study had two cohorts: those who were taking preexposure prophylaxis (PrEP) against human immunodeficiency virus (HIV) infection (PrEP cohort) and persons living with HIV infection (PLWH cohort). Within each cohort, participants in the doxycycline group were assigned to take doxycycline within 72 hours after condomless sex (doxycycline postexposure prophylaxis, or doxy-PEP]), and participants in the standard-care group were assigned to receive standard care without doxycycline. The modified intention-to-treat population includes all the participants with at least one follow-up visit expected by May 13, 2022 (date of early discontinuation of the standard-care groups by the data and safety monitoring board). GHB denotes γ-hydroxybutyrate, IQR interquartile range, and STI sexually transmitted infection.
Race and ethnic group were reported by the participant.
Syphilis includes only primary, secondary, or early latent syphilis.
Transactional sex includes either paying for sex or being paid for sex.