Evaluating the impact of policies recommending PrEP to subpopulations of men and transgender women who have sex with men based on demographic and behavioral risk factors

Introduction
Developing guidelines to inform the use of antiretroviral pre-exposure prophylaxis (PrEP) for HIV prevention in resource-limited settings must necessarily be informed by considering the resources and infrastructure needed for PrEP delivery. We describe an approach that identifies subpopulations of cisgender men who have sex with men (MSM) and transgender women (TGW) to prioritize for the rollout of PrEP in resource-limited settings.
Methods
We use data from the iPrEx study, a multi-national phase III study of PrEP for HIV prevention in MSM/TGW, to build statistical models that identify subpopulations at high risk of HIV acquisition without PrEP, and with high expected PrEP benefit. We then evaluate empirically the population impact of policies recommending PrEP to these subpopulations, and contrast these with existing policies.
Results
A policy recommending PrEP to a high risk subpopulation of MSM/TGW reporting condomless receptive anal intercourse over the last 3 months (estimated 3.3% 1-year HIV incidence) yields an estimated 1.95% absolute reduction in 1-year HIV incidence at the population level, and 3.83% reduction over 2 years. Importantly, such a policy requires rolling PrEP out to just 59.7% of MSM/TGW in the iPrEx population. We find that this policy is identical to that which prioritizes MSM/TGW with high expected PrEP benefit. It is estimated to achieve nearly the same reduction in HIV incidence as the PrEP guideline put forth by the US Centers for Disease Control, which relies on the measurement of more behavioral risk factors and which would recommend PrEP to a larger subset of the MSM/TGW population (86% vs. 60%).
Conclusions
These findings may be used to focus future mathematical modelling studies of PrEP in resource-limited settings on prioritizing PrEP for high-risk subpopulations of MSM/TGW. The statistical approach we took could be employed to develop PrEP policies for other at-risk populations and resource-limited settings.

# 引言
为制定指导资源有限地区使用抗逆转录病毒暴露前预防（PrEP）开展人类免疫缺陷病毒（HIV）预防的指南，必须充分考量PrEP实施所需的资源与基础设施条件。本研究描述了一种筛选方法，可识别顺性别男男性行为者（MSM）与跨性别女性（TGW）中的亚人群，用于在资源有限地区优先推广PrEP。

# 方法
本研究使用iPrEx研究的数据开展分析。iPrEx是一项针对MSM/TGW人群开展HIV预防的多国多中心III期PrEP临床试验。我们构建统计模型，以识别未使用PrEP时HIV感染风险较高、且预期PrEP获益显著的亚人群。随后，我们通过实证分析针对上述亚人群推荐PrEP的政策的人群层面影响，并与现有政策进行对比。

# 结果
针对近3个月报告有无保护性被动肛交行为的高风险MSM/TGW亚人群（估计年HIV感染率为3.3%）推荐PrEP的政策，可使人群水平的1年HIV感染率绝对降低1.95个百分点，2年内累计绝对降低3.83个百分点。值得注意的是，该政策仅需在iPrEx研究人群中的59.7%的MSM/TGW中推广PrEP。我们发现，该政策与优先为预期PrEP获益较高的MSM/TGW人群推广PrEP的策略完全一致。据估算，该政策实现的HIV感染率降低幅度，与美国疾病控制与预防中心（CDC）发布的PrEP预防指南几乎相当；后者需通过更多行为风险因素评估来确定推荐人群，覆盖的MSM/TGW人群比例更高（86% vs 60%）。

# 结论
本研究结果可用于指导未来在资源有限地区开展的PrEP数学建模研究，聚焦为高风险MSM/TGW亚人群优先配置PrEP资源。本研究采用的统计方法，亦可用于为其他高危人群及资源有限地区制定PrEP相关政策。