NEEMA Funded Projects - STD

NEEMA 3.0 (2024-2029)

Impact on disease prevalence and antimicrobial resistance of post-exposure doxycycline prophylaxis

Emerging data from clinics in the United States (U.S.) indicate that doxycycline post-exposure prophylaxis (doxy PEP) is associated with declines in sexually transmitted infections (STIs), particularly chlamydia and syphilis, among men who have sex with men (MSM). However, the population-level impact of doxy PEP on gonorrhea, chlamydia, and syphilis has not been well characterized, and there is concern that increased use could lead to the emergence of resistance in Neisseria gonorrhoeae. This project will adapt an existing mathematical model of gonorrhea transmission among MSM to also incorporate chlamydia and syphilis, enabling estimation of the potential impact of doxy PEP on all three infections. The objectives of this project are to 1) estimate the reduction in gonorrhea incidence and changes in doxycycline resistance among users and non-users of doxy PEP; 2) compare surveillance strategies in their ability to identify increases in doxycycline resistance among users and non-users of doxy PEP; and 3) estimate the reduction in gonorrhea incidence with the rollout of a partially effective gonorrhea vaccine and identify the level of uptake needed to counter the reduced effectiveness of doxy PEP in settings with high levels of doxycycline resistance. By quantifying the potential population-level benefits of doxy PEP across multiple STIs, this project fills a key evidence gap needed to guide clinical and public health decision-making around doxy PEP implementation. Findings will be disseminated through multiple channels to inform STI prevention strategies for MSM nationally.

Lifetime health impact and direct medical cost per case of congenital syphilis, stratified by treatment status at birth

Congenital syphilis (CS) cases have risen sharply in the United States. Up-to-date estimates of the lifetime health and economic burden of CS are needed to support cost-effectiveness analyses of prevention interventions and programs. Existing estimates may not fully capture the range of birth outcomes and treatment scenarios associated with CS, nor the productivity costs borne by parents and guardians in addition to affected infants. This project will use a decision tree model, informed entirely by existing published literature, to estimate the average lifetime direct medical cost, lifetime productivity cost, and quality-adjusted life years lost per case of CS. The model will account for all combinations of birth outcomes (stillbirth, neonatal death, symptomatic infant, asymptomatic infant) and infant treatment status (treated versus not treated at birth), incorporating epidemiologic parameters (probability and duration of health outcomes) and economic parameters (medical and productivity costs) across the lifespan of affected infants and their parents. By generating comprehensive, updated estimates of CS-related costs and health impacts, this project fills a critical gap needed to inform cost-effectiveness studies and burden-of-disease assessments related to syphilis and CS prevention efforts in the United States.

Strategies to reduce congenital syphilis incidence in disproportionately affected populations

Congenital syphilis (CS) disproportionately affects certain populations in the United States, underscoring the need to evaluate which prevention strategies are most effective both at the population level and among disproportionately affected groups. While intervention strategies exist, evidence on their differential health impact across populations remains limited, making it difficult to prioritize approaches that address existing disparities. This project will evaluate the health impacts of strategies designed to prevent congenital syphilis. The primary goal is to quantify the health impact of prevention strategies both overall and within specific disproportionately affected populations. Specific objectives include (1) estimating the total reduction in CS incidence at the population level, and (2) estimating the reduction in CS incidence within specific populations affected. By quantifying differential impacts across populations, this project fills a gap in understanding which strategies most effectively reduce CS disparities.

Estimating effects of multi-infection prevention and diagnosis approaches for HIV and bacterial sexually transmitted infections among men who have sex with men

CDC recommends routine screening for syphilis, gonorrhea, and chlamydia alongside HIV testing for sexually active men who have sex with men (MSM), particularly those at higher risk or on HIV pre-exposure prophylaxis (PrEP). However, sexually transmitted infection (STI) screening is not automatically bundled with HIV testing, and screening rates remain below recommended levels, especially in non-hospital settings. This gap contributes to missed diagnoses amid rising syphilis incidence, continued evolution of drug-resistant gonorrhea, and a substantial proportion of MSM unaware of their HIV status. This project will use an agent-based microsimulation model to evaluate the potential impact of integrated HIV and bacterial STI screening among MSM under a syndemic approach. Primary objectives include estimating the epidemic impact of integrated screening and evaluating how coordinated diagnosis and treatment of HIV, syphilis, chlamydia, and gonorrhea affects infection incidence. The project will generate outputs such as infections averted per 1,000 tests to support cost-effectiveness analyses. By quantifying the benefits of integrated screening, this project fills a critical gap in evidence needed to improve testing practices and inform public health strategies to control HIV and STI transmission among MSM.

Impact of jail implementation of the CDC screening and treatment recommendations for correctional settings on national and state prevalence of hepatitis C and syphilis

People who are justice system-involved experience higher rates of hepatitis C and sexually transmitted infections than the general population, and correctional health services are often their first or only touchpoint for testing and treatment. CDC recommends comprehensive opt-out testing at intake, treatment during incarceration, and linkage to care upon release for incarcerated individuals, but staffing, budget constraints, rapid turnover of the incarcerated population, and limited collaboration with local health departments create significant barriers to full implementation. Since 95% of incarcerated individuals return to their communities, successful implementation could meaningfully reduce community disease prevalence and transmission. This project will estimate changes in national and state hepatitis C and syphilis incidence, along with associated health and economic outcomes, if all U.S. adult jails fully implemented the CDC Recommendations for Correctional Settings. Using a model incorporating national epidemiologic estimates, correctional statistics, and intervention effectiveness data, the project will evaluate scenarios reflecting varying levels of implementation and community background testing and treatment rates, along with associated costs and sensitivity analyses across the care continuum. By quantifying the potential population-level and economic benefits of full implementation, this project fills a critical gap in understanding how correctional health interventions could reduce disease transmission and disparities, informing investment and program decisions.