Table 3.
Incidence and risk of HIV-1 infection, by injection type
| Number of HIV-1 seroconversions/person-years | Incidence per 100 person-years (95% CI) | Unadjusted Cox proportional hazards regression analysis
|
Adjusted Cox proportional hazards regression analysis
|
|||
|---|---|---|---|---|---|---|
| Hazard ratio (95% CI) | p value | Hazard ratio (95% CI) | p value | |||
|
Primary comparison in whole cohort (n=3141)
| ||||||
| NET-EN | 55/970·8 | 5·67 (4·35–7·38) | Reference | ·· | Reference | ·· |
| DMPA | 152/1763·0 | 8·62 (7·35–10·11) | 1·53 (1·12–2·08) | 0·007 | 1·41 (1·06–1·89)* | 0·02 |
| Total | 207/2733·7 | 7·57 (6·61–8·68) | ·· | ·· | ·· | ·· |
|
| ||||||
|
Women who reported no condom use for vaginal sex at baseline (n=304)
| ||||||
| NET-EN | 1/104·8 | 0·95 (0·13–6·77) | Reference | ·· | Reference | ·· |
| DMPA | 7/163·2 | 4·29 (2·05–9·00) | 4·80 (0·59–39·13) | 0·1 | 3·92 (1·36–11·28)† | 0·01 |
| Total | 8/268·0 | 2·98 (1·49–5·97) | ·· | ·· | ·· | ·· |
|
| ||||||
|
Women under 25 years old at baseline (n=1890)
| ||||||
| NET-EN | 41/625·1 | 6·56 (4·83–8·91) | Reference | ·· | Reference | ·· |
| DMPA | 104/975·7 | 10·66 (8·80–12·92) | 1·63 (1·14–2·35) | 0·008 | 1·40 (1·01–1·95) | 0·05 |
| Total | 145/1600·8 | 9·06 (7·70–10·66) | ·· | ·· | ·· | ·· |
|
| ||||||
|
Women who were HSV-2 seronegative at baseline (n=1671)‡
| ||||||
| NET-EN | 34/578·5 | 5·88 (4·20–8·23) | Reference | ·· | Reference | ·· |
| DMPA | 55/866·6 | 6·35 (4·87–8·27) | 1·08 (0·70–1·65) | 0·7 | 1·09 (0·78–1·52)§ | 0·6 |
| Total | 89/1445·0 | 6·16 (5·00–7·58) | ·· | ·· | ·· | ·· |
|
| ||||||
|
Women who were HSV-2-seropositive at baseline (n=1459)‡
| ||||||
| NET-EN | 21/387·2 | 5·42 (3·54–8·32) | Reference | ·· | Reference | ·· |
| DMPA | 97/895·4 | 10·83 (8·88–13·22) | 2·02 (1·26–3·24) | 0·003 | 2·01 (1·12–3·63)§ | 0·02 |
| Total | 118/1282·5 | 9·20 (7·68–11·02) | ·· | ·· | ·· | ·· |
|
| ||||||
|
Whole cohort plus women with injectable exposure and person-time following pregnancy outcomes (n=3208)
| ||||||
| NET-EN | 56/983·1 | 5·70 (4·38–7·40) | Reference | ·· | Reference | ·· |
| DMPA | 155/1787·8 | 8·67 (7·41–10·15) | 1·53 (1·13–2·08) | 0·006 | 1·42 (1·04–1·95)* | 0·03 |
| Total | 211/2770·9 | 7·61 (6·65–8·71) | ·· | ·· | ·· | ·· |
|
| ||||||
|
Women with trichomonas, chlamydia, or gonorrhoea infection at baseline (n=671)
| ||||||
| NET-EN | 17/201·0 | 8·46 (5·26–13·60) | Reference | ·· | Reference | ·· |
| DMPA | 59/376·8 | 15·66 (12·13–20·21) | 1·86 (1·08–3·19) | 0·02 | 1·79 (1·16–2·75)* | 0·008 |
| Total | 76/577·8 | 13·15 (10·51–16·47) | ·· | ·· | ·· | ·· |
|
| ||||||
|
Women who used both DMPA and NET-EN at different times during follow-up (n=256)
| ||||||
| NET-EN | 3/104·2 | 2·88 (0·93–8·92) | Reference | ·· | Reference | ·· |
| DMPA | 18/146·5 | 12·29 (7·74–19·50) | 4·82 (1·41–16·51) | 0·01 | 4·76 (2·15–10·52)* | 0·0001 |
| Total | 21/250·7 | 8·38 (5·46–12·85) | ·· | ·· | ·· | ·· |
|
| ||||||
|
Women who did not switch between DMPA and NET-EN during follow-up (n=2885)
| ||||||
| NET-EN | 52/866·6 | 6·00 (4·57–7·87) | Reference | ·· | Reference | ·· |
| DMPA | 134/1616·5 | 8·29 (7·00–9·82) | 1·40 (1·01–1·92) | 0·04 | 1·29 (0·94–1·76)* | 0·1 |
| Total | 186/2483·0 | 7·49 (6·49–8·65) | ·· | ·· | ·· | ·· |
DMPA=depot medroxyprogesterone acetate. HSV-2=herpes simplex virus type 2. NET-EN=norethisterone enanthate.
Adjusted for baseline age, marriage or cohabitation, education, and HSV-2 status, and time-varying oral contraceptive pill use, primary partner has other partners, and condom use at last sex, with stratification by study site.
Adjusted for baseline age, marriage or cohabitation, education, and HSV-2 status, and time-varying oral contraceptive pill use, and primary partner has other partners, with stratification by study site.
Baseline HSV-2 status was available for 3130 (99·6%) of the cohort.
Adjusted for baseline age, marriage or cohabitation, and education, and time-varying oral contraceptive pill use, primary partner has other partners, and condom use at last sex, with stratification by study site.