BACKGROUND Outcomes in observational studies may not best estimate those expected in the HIV vaccine efficacy trials. We compared retention in Simulated HIV Vaccine Efficacy Trials (SiVETs) and observational cohorts drawn from two key populations in Uganda. METHODS Two SiVETs were nested within two observational cohorts, one in Fisherfolk (FF) and another one in Female Sex Workers (FSW). Adult participants in each observational cohort were screened for enrolment into SiVETs. Those screened-out or not screened continued participation in the observational (non-SiVET) cohorts. SiVET participants were administered a licensed hepatitis B vaccine in a schedule that mimicked an actual HIV vaccine efficacy trial. Both cohorts were followed for 12 months and retention was assessed through dropout, defined as lost to follow up, being uncontactable, refusal to continue or missing the last study clinic visit. Dropout rates were compared using Poisson models giving rate ratios and 95% confidence intervals (95%CI). RESULTS Out of 1525 participants (565 FF and 960 FSW), 572 (38%) were enrolled into SiVETs (282-FF and 290-FSW), and 953 (62%) remained in the non-SiVET cohorts. Overall, 326 (101 SiVET, 225 non-SiVET) dropped out in 1260 Person Years of Observation (PYO), a dropout rate of 25.9 /100 PYO (95%CI: 23.2-28.8); fewer dropped out in the SiVET cohorts (18.4, 95% CI: 15.1-22.4) than in the non-SiVET cohorts (31.6, 95% CI: 27.8-36.1), rate ratio (RR) =0.58, 95% CI: 0.46-0.73. In all cohorts, the dropout was more marked in FSW than in FF population. Duration lived in community was associated with dropout in both SiVETs and religion in both non-SiVET cohorts. CONCLUSION The rate of dropout was lower in SiVET compared to non-SiVET cohort. Though the difference in dropout between SiVET and non-SiVET was generally similar, the actual dropout rates were higher in the FSW population. Conduct of SiVETs in these key populations could mean that designing HIV Vaccine Efficacy Trials will benefit from lower dropout rate shown in SiVET than non-SiVET observational cohort.

中文翻译：

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在乌干达主要人群中观察性队列保留率和嵌套式模拟HIV疫苗功效试验的保留率比较。

背景技术观察性研究的结果可能无法最佳地估计HIV疫苗功效试验中预期的结果。我们比较了模拟艾滋病毒疫苗功效试验（SiVET）和从乌干达的两个主要人群中获得的观察性队列的保留率。方法将两个SiVET嵌套在两个观察性队列中，一个在Fisherfolk（FF）中，另一个在女性性工作者（FSW）中。对每个观察队列的成年参与者进行筛查以纳入SiVET。那些筛选出或未筛选出的人继续参加观察性（非SiVET）人群。SiVET参与者按照模仿实际HIV疫苗功效试验的时间表接受了许可的乙肝疫苗的接种。两组均随访了12个月，并通过辍学评估了保留率，定义为失访，无法联系，拒绝继续或错过上一次研究诊所就诊。使用泊松模型比较了辍学率，给出了比率和95％的置信区间（95％CI）。结果在1525名参与者（565 FF和960 FSW）中，有572名（38％）被纳入SiVET（282-FF和290-FSW），而953名（62％）仍留在非SiVET队列中。总体而言，在1260人观察年（PYO）中有326（101 SiVET，225非SiVET）退学，辍学率为25.9 / 100 PYO（95％CI：23.2-28.8）; 与非SiVET队列（31.6，95％CI：27.8-36.1）相比，SiVET队列（18.4，95％CI：15.1-22.4）更少，比率（RR）= 0.58，95％CI：0.46 -0.73。在所有队列中，FSW的辍学率均比FF人群高。在两个非SiVET人群中，社区生活的持续时间与SiVET的辍学和宗教信仰有关。结论与非SiVET队列相比，SiVET的辍学率较低。尽管SiVET和非SiVET的辍学差异大致相似，但FSW人群的实际辍学率更高。在这些关键人群中开展SiVET可能意味着，与非SiVET观察人群相比，SiVET中显示出的辍学率更低，这将有助于设计HIV疫苗效力试验。