Table 2.
HIV incidence estimates (including unadjusted hazard ratios [HR]) over the 2008–2020 period among different population groups, and by different stratifications among PWID attending the drop-in centres in Kachin.
| Group | Baseline population size (n=) | Total person years of follow-up (yr) | Number of HIV infections (n=) | Rate per 100 py | 95% CI | HR (unadjusted) | 95% CI | p-value |
|---|---|---|---|---|---|---|---|---|
| Total | 3685 | 8976.2 | 473 | 5.3 | 4.8–5.8 | n/a | ||
| PWUD | 692 | 1295.2 | 13 | 1.0 | 0.6–1.7 | 1 | ||
| non-PWUD | 716 | 1414.4 | 16 | 1.1 | 0.7–1.8 | 1.24 | 0.62–2.48 | 0.548 |
| PWID | 2277 | 6266.5 | 444 | 7.1 | 6.5–7.8 | 7.68 | 4.59–12.85 | <0.001 |
| Male | 2896 | 7288.42 | 447 | 6.1 | 5.6–6.7 | 1 | ||
| Female | 789 | 1687.7 | 26 | 1.5 | 1.0–2.3 | 0.25 | 0.17–0.38 | <0.001 |
| Among PWID only | ||||||||
| Male PWID | 2246 | 6173.4 | 436 | 7.1 | 6.4–7.8 | 1 | ||
| Female PWID | 31 | 93.1 | 8 | 8.6 | 4.3–17.2 | 1.21 | 0.60–2.43 | 0.601 |
| Age <25 yrs | 777 | 1587.1 | 152 | 9.6 | 8.2–11.2 | 1 | ||
| Age ≥25 yrs | 1500 | 4679.5 | 292 | 6.2 | 5.6–7.0 | 0.69 | 0.60–0.83 | <0.001 |
| Hopin | 773 | 2144.8 | 139 | 6.5 | 5.5–7.7 | 1 | ||
| Mogaung | 962 | 3076.8 | 186 | 6.0 | 5.2–7.0 | 0.95 | 0.76–1.18 | 0.646 |
| Myitkyina | 542 | 1044.9 | 119 | 11.4 | 9.5–13.6 | 1.73 | 1.35–2.21 | <0.001 |
| 2008–2011 | 365 | 139.6 | 27 | 19.3 | 13.3–28.2 | 1 | ||
| 2012–2016 | 975 | 1253.7 | 165 | 13.2 | 11.3–15.3 | 0.66 | 0.44–1.00 | 0.053 |
| 2017–2020 | 937 | 4873.3 | 252 | 5.2 | 4.6–5.9 | 0.28 | 0.18–0.42 | <0.001 |
| Length of follow-up <3 yrs | 2277 | 2468.4 | 262 | 10.6 | 9.4–12.0 | 1 | ||
| Length of follow-up ≥3 yrsa | 0 | 3798.1 | 182 | 4.8 | 4.1–5.5 | 0.37 | 0.28–0.49 | <0.001 |
| Injected within 6 wks | 941 | 1769.2 | 216 | 12.2 | 10.7–14.0 | 1.50 | 1.21–1.87 | <0.001 |
| Not injected within 6 wks | 829 | 1523.0 | 126 | 8.3 | 6.9–9.9 | 1 | ||
| No response recordedb | 507 | 2974.4 | 102 | 3.4 | 2.8–4.2 | 0.44 | 0.33–0.57 | <0.001 |
| Shared needles within 6 wks | 211 | 331.2 | 61 | 18.4 | 14.3–23.7 | 1.92 | 1.46–2.54 | <0.001 |
| Not shared within 6 wks | 1594 | 2898.6 | 281 | 9.7 | 8.6–10.9 | 1 | ||
| No response recordedb | 472 | 3036 | 102 | 3.4 | 2.8–4.0 | 0.36 | 0.29–0.46 | <0.001 |
| Unsafe sex within 6 wks | 71 | 227.8 | 21 | 9.2 | 6.0–14.1 | 1.76 | 1.12–2.76 | 0.014 |
| Not had unsafe sex within 6 wks | 611 | 3,625.5 | 189 | 5.2 | 4.5–6.0 | 1 | ||
| No response recorded | 1595 | 2413.2 | 234 | 7.0 | 8.5–11.0 | 1.73 | 1.42–2.11 | <0.001 |
| NSP lowc | 399 | 707.8 | 74 | 10.5 | 8.3–13.1 | 1.19 | 0.91–1.54 | 0.199 |
| NSP mediumc | 1059 | 2622.7 | 229 | 8.7 | 7.6–9.9 | 1 | ||
| NSP highc | 454 | 2796.4 | 114 | 4.1 | 3.4–4.9 | 0.49 | 0.39–0.61 | <0.001 |
| Reports no polydrug used | 1847 | 3230.5 | 326 | 10.1 | 9.1–11.2 | 0.87 | 0.57–1.32 | 0.511 |
| Reports polydrug used | 150 | 277.1 | 24 | 8.7 | 5.8–12.9 | 1 | ||
| No response recorded | 280 | 2758.9 | 94 | 3.4 | 2.8–4.2 | 0.35 | 0.28–0.45 | <0.001 |
| IDU duration <2 yrse | 221 | 73.4 | 22 | 30.0 | 19.7–45.5 | 1 | ||
| IDU duration 2–<5 yrse | 666 | 752.3 | 133 | 17.7 | 14.9–21.0 | 0.48 | 0.30–0.76 | 0.002 |
| IDU duration 5–<10 yrse | 544 | 2061.5 | 136 | 6.6 | 5.6–7.8 | 0.17 | 0.10–0.27 | <0.001 |
| IDU duration ≥10 yrse | 372 | 2233.3 | 85 | 3.8 | 3.1–4.7 | 0.10 | 0.06–0.17 | <0.001 |
| No response recorded | 474 | 1146.0 | 68 | 5.9 | 4.7–7.5 | 0.16 | 0.09–0.26 | <0.001 |
| Never on OAT during follow-upf | 1140 | 2376.4 | 231 | 9.7 | 8.5–11.1 | 1 | ||
| Prior to starting OATf | 1036 | 1117.0 | 115 | 10.3 | 8.6–12.4 | 1.04 | 0.83–1.30 | 0.741 |
| After OAT stoppedf | 0 | 217.7 | 19 | 8.7 | 5.6–13.7 | 0.92 | 0.58–1.47 | 0.728 |
| Currently on OATf | 101 | 2555.4 | 79 | 3.1 | 2.5–3.9 | 0.33 | 0.26–0.43 | <0.001 |
The population size of time-varying factors (including time period, length of follow-up, needle and syringe provision [NSP]) is based on the baseline (at enrolment). For some factors on injecting behaviour, a large number of people with no response were observed; these groups generally had the lowest incidence, aligning with the fact that these risk behaviour questions were asked of PWID that were thought to be higher risk.
Baseline was client enrolment, and length of follow up at this time was by definition 0 years. At the end of the study, 859 PWID were followed for >3 years.
25.1% of PWID were not asked if they had injected within the last 6 weeks, and 45.6% were not asked if they had shared needles in the last 6 weeks.
Needle and syringe provision (NSP) coverage was defined by calculating the median coverage over 6-month periods between 2012 and 2020. A low coverage period was assigned if the number of syringes distributed was below the lower quartile of the 6-monthly number of syringes distributed over 2012–2020, while a high coverage period was assigned if the number of syringes distributed was above the upper quartile; otherwise, the period was assigned as being medium coverage (see Supplementary Table S1).
Polydrug use was recorded as ‘yes’ for PWID taking multiple different classes of drugs. This was typically heroin or other opiates plus either amphetamines, yama (a mixture of methamphetamine and caffeine widely used in South East Asia) or alcohol. The majority of PWID in the study reported taking either heroin and/or opiates, which were considered the same drug class and recorded as ‘no polydrug use’.
Injecting drug use (IDU) duration was calculated by taking the self-reported duration at the first recorded HIV test and adding the length of time followed-up after this.
Considerable scale-up of OAT was observed throughout the study. By the end of the study, 260 PWID were recorded going onto OAT at a later time point, 81 PWID had stopped taking OAT, and 859 were currently taking OAT. For the analysis of OAT, ‘Prior to starting OAT’ includes all test records of PWID that take OAT during follow-up but have not started yet. ‘After OAT stopped’ includes all test records of PWID that take OAT during follow-up but have now stopped taking OAT. ‘Never on OAT during follow-up’ includes test records of PWID who never took OAT. ‘Currently on OAT’ includes the test records of PWID after their start date of taking OAT and excludes test records of PWID after they discontinued OAT.