Stanford
Prevention Policy Modeling Lab

HIV

Research Area

HIV

Click on a project title to learn more about PPML's work on HIV.

Current Projects

Diagnosing HIV infections as early as possible is central to Ending the HIV Epidemic in the U.S. (EHE) goals. This project proposes to estimate where in the U.S. increasing HIV screening would be most beneficial. The benefits of different HIV testing strategies will be evaluated by state, populations (MSM, MSW, WSM, PWID), and age groups.

The overall aim is to estimate effects of different testing approaches to address unmet need for knowledge of HIV serostatus. Research questions include:  

  • What is the capability of the current levels of testing to identify new HIV infections?
  • How many new HIV infections are potentially missed by current testing?
  • Which testing strategy would identify the most HIV infections?

As health departments face resource constraints and harm reduction services in some areas face social and political pushback, there is a risk of reduced access to these evidence-based services.

The primary goal of this modeling project is to estimate the health and economic consequences of reduced access to and use of SSP and MOUD among people who inject drugs. Utilizing PPML’s previously developed sexual and injection network model, this project will also evaluate the impact of reduced access and use of SSPs and MOUD on HIV and HCV transmission.

PPML is supporting an update to the National Vulnerability Assessment for health outcomes associated with injection drug use (IDU). The updated national vulnerability assessment will address the main study question:

  • What factors are associated with unsterile IDU nationally and what areas are most at risk for the negative health outcomes associated with IDU?

PPML will develop and apply a framework for designing and evaluating vulnerability assessments and other surveillance metrics using the analogy of a decision analysis for a diagnostic test. These consequences will highlight the need to connect these assessments and surveillance metrics to specific public health actions that are triggered by positive or negative signals. We have previously developed a related framework and analytic tools for COVID-19 surveillance metrics, which are being adapted for this project in view of the specific assessments and metrics that are the focus.

This project will align the national and state vulnerability assessments to develop a consistent evaluation method.

Past Projects

Persons who inject drugs (PWID) are at high risk for multiple bloodborne and sexually transmitted infections, including hepatitis C virus (HCV) and HIV. National and state-level planning for syringe service programs (SSP) and medication for opioid use disorder (MOUD) relies on the accurate estimation of PWID population size and requires an understanding of how these interventions impact HCV and HIV transmission, in addition to other bloodborne infections. The structure of injection and sexual networks among PWID leads to heterogeneous risks of infection transmission and acquisition. In addition to SSPs and MOUD, many other preventive strategies are available for both HCV and HIV, including biomedical interventions, such as HIV pre-exposure prophylaxis, HIV treatment, HCV treatment, and behavioral interventions, such as promoting safer injection practices and condom use. Interventions can interact and generate synergistic effects on the prevention of HCV and HIV. What determines the optimal intervention package is unknown. 

This project extended PPML’s existing agent-based network model of HCV transmission among PWID by adding the sexual partnership network and transmission dynamics of HIV and other sexually transmitted infections to the existing network of equipment-sharing.

Further expansion of this work integrated detailed clinical and program data from Massachusetts into the agent-based multiplex model and provides insight into specific questions through a partnership with the Massachusetts Department of Public Health.

Awareness of PrEP for HIV and knowledge of its effectiveness have increased in recent years. PrEP is recommended for people at high risk of HIV acquisition and is a crucial component in the Ending the HIV Epidemic in the U.S. (EHE) Initiative. To develop more accurate PrEP coverage indicators, an estimate is needed to quantify the population who can benefit from PrEP. Given advances in PrEP use for HIV prevention, the current definition of PrEP need may be too restrictive. 

This project re-evaluated the population size of people who could benefit from PrEP and developed a revised metric for PrEP need in the United States.

HIV testing is an integral component of the Ending the HIV Epidemic in the U.S. (EHE) Initiative, specifically the Diagnose pillar. Estimating and evaluating the reach of HIV testing efforts allows national, state, and local partners to make informed decisions to improve access and reach of HIV testing. 

The project summarized key HIV measures with a focus on testing needs and uptake, including coverage of HIV testing over time, HIV tests performed annually in the U.S., and people who should be tested for HIV following CDC recommendations.

In 2006, CDC recommended routine HIV testing for adolescents and adults, ages 13 to 64, in the United States. These recommendations were based on several factors and studies, including the overall and undiagnosed prevalence of HIV in the United States, the availability, accuracy, rapidity, and low cost of the HIV test, and the availability of highly effective and life-saving therapies for HIV. Model-based analyses suggested that routine HIV testing would be very cost-effective, although these analyses did not include adolescents specifically.

The current CDC recommendations are based on a model using case surveillance among those aged 13 and over. While the recommendations imply that it is worthwhile to get tested at least once in a lifetime, this recommendation is difficult to interpret early in the life course. National data highlight that HIV prevalence varies across age groups and is much lower in teens than in young and older adults. For these reasons, there is an important need to further refine the lower end of the age range for HIV testing guidelines.

This project examined the yield, cost, and cost-effectiveness of routine HIV testing in school-aged adolescents and young adults in the United States.

Associated Publication