Achieving the "Ending the HIV Epidemic in the U.S." incidence reduction goals among at-risk populations in the South

Modelling HIV/AIDS epidemiological complexity: A scoping review of Agent-Based Models and their application

OBJECTIVE

To end the AIDS epidemic by 2030, despite the increasing poverty and inequalities, policies should be designed to deal with population heterogeneity and environmental changes. Bottom-up designs, such as the Agent-Based Model (ABM), can model these features, dealing with such complexity. HIV/AIDS has a complex dynamic of structural factors, risk behaviors, biomedical characteristics and interventions. All embedded in unequal, stigmatized and heterogeneous social structure. To understand how ABMs can model this complexity, we performed a scoping review of HIV applications, highlighting their potentialities.

METHODS

We searched on PubMed, Web of Science, and Scopus repositories following the PRISMA extension for scoping reviews. Our inclusion criteria were HIV/AIDS studies with an ABM application. We identified the main articles using a local co-citation analysis and categorized the overall literature aims, (sub)populations, regions, and if the papers declared the use of ODD protocol and limitations.

RESULTS

We found 154 articles. We identified eleven main papers, and discussed them using the overall category results. Most studies model Transmission Dynamics (37/154), about Men who have sex with Men (MSM) (41/154), or individuals living in the US or South Africa (84/154). Recent studies applied ABM to model PrEP interventions (17/154) and Racial Disparities (12/154). Only six papers declared the use of ODD Protocol (6/154), and 34/154 didn't mention the study limitations.

CONCLUSIONS

While ABM is among the most sophisticated techniques available to model HIV/AIDS complexity. Their applications are still restricted to some realities. However, researchers are challenged to think about social structure due model characteristics, the inclusion of these features is still restricted to case-specific. Data and computational power availability can enhance this feature providing insightful results.

Modeling the impact of changing sexual behaviors with opposite-sex partners and STI testing among women and men ages 15-44 on STI diagnosis rates in the United States 2012-2019

Objective

To estimate the potential contributions of reported changes in frequency of penile-vaginal sex (PVS), condom use and STI screening to changes in gonorrhea and chlamydial diagnoses from 2012 to 2019.

Methods

An agent-based model of the heterosexual population in the U.S. simulated the STI epidemics. Baseline was calibrated to 2012 diagnosis rates, testing, condom use, and frequency of PVS. Counterfactuals used behaviors from the 2017-2019 NSFG, and we evaluated changes in diagnosis and incidence rates in 2019.

Results

Higher testing rates increased gonorrhea and chlamydia diagnosis by 14% and 13%, respectively, but did not reduce incidence. Declining frequency of PVS reduced the diagnosis rate for gonorrhea and chlamydia 6% and 3% respectively while reducing incidence by 10% and 9% respectively. Declining condom use had negligible impact on diagnosis and incidence.

Conclusion

Understanding how changing behavior drives STI incidence is essential to addressing the growing epidemics. Changes in testing and frequency of PVS likely contributed to some, but not all, of the changes in diagnoses. More research is needed to understand the context within which changing sexual behavior and testing are occurring.

Potential contribution of PrEP uptake by adolescents 15-17 years old to achieving the "Ending the HIV Epidemic" incidence reduction goals in the US South

BACKGROUND

The "Ending the HIV Epidemic" (EHE) initiative seeks to reduce new HIV infections in the U.S. by prioritizing federal resources towards highly impacted populations. Antiretroviral therapy (ART) and pre-exposure prophylaxis (PrEP) are essential for reaching EHE goals. Adolescents are often at increased risk for HIV because they may lack agency in negotiating their sexual partnerships and may not have the same access to treatment and prevention as adults. This study estimates the potential contribution of expanded PrEP coverage among adolescents ages 15-17 to achieving the EHE goals in the South.

METHODS

An HIV-transmission model was built to simulate the HIV epidemic in the South. Increased ART and PrEP uptake were systematically varied with and without PrEP eligibility including individuals age<18.

RESULTS

Prioritizing PrEP for adolescents had a negligible impact on incidence. At 50% uptake among eligible adolescents and 90% ART coverage, including adolescents only improved the percentage of infections averted from 80.1% to 80.3%. In 10 of 15 scenarios explored, there was no reduction in new infections when PrEP eligibility was expanded to include adolescents age<18. At 95% ART coverage at the population-level incidence among adolescents declined by over 80%, but PrEP uptake among adolescents did not contribute to additional declines in incidence among adolescents.

CONCLUSIONS

Prioritizing PrEP for adolescents did not significantly contribute to reaching EHE incidence reductions goal. Focusing resources to specific adolescent populations at risk, such sexual minority males in high incidence settings, will remain an important public health goal outside the context of EHE.