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SHIELD Project

Syphilis & HIV Dynamics

Research Methodology

The SHIELD project develops a comprehensive modeling framework to understand and address the rising syphilis epidemic in the United States, particularly its intersection with HIV.

SHIELD Model Structure

Our model defines population compartments along three main axes:

  • Syphilis natural history - tracking infection stages and progression
  • Syphilis care cascade - modeling screening, diagnosis, and treatment
  • HIV care continuum - incorporating HIV status and care engagement

These compartments are further stratified by:

  • Age - focusing on key age groups with differential risk
  • Race/ethnicity - to capture disparities in disease burden
  • STI risk - including MSM, heterosexual activity, injection drug use, and pregnancy status
  • Social determinants of health - incorporating factors like insurance coverage and housing instability

Calibration Approach

We use a Bayesian calibration approach that:

Combines prior knowledge about factors underpinning US syphilis epidemics with local-level data

Quantifies uncertainty in parameter estimates

Generates a range of possible epidemic projections

Yields estimates that are robust to model assumptions and inherent unknowns in surveillance

Research Aims

1

Assessing Existing Control Strategies

We evaluate combinations of improvements in syphilis testing, partner tracing, and treatment initiation among subgroups of people with HIV (PWH) and other priority subgroups (MSM and pregnant women).

Key activities include:

  • Projecting the interventions' impact on future trajectory and health disparities
  • Estimating the interventions' cost-effectiveness
  • Identifying the most impactful and cost-effective intervention combinations for each city
2

Projecting the Impact of Emerging Strategies

We simulate novel prevention and diagnostic approaches including:

Doxycycline post-exposure prophylaxis (doxy-PEP) - at various levels of uptake, persistence, and effectiveness
Novel testing strategies - including at-home sample collection, point-of-care testing, and nucleic acid amplification tests

We identify scenarios that are most impactful while remaining cost-effective, and explore combinations with existing approaches that can reduce racial/ethnic disparities in syphilis incidence.

3

Developing a Decision Support Toolkit

We are developing an online toolkit to help local decision-makers:

Design syphilis interventions based on local epidemiology

Consider budgetary constraints in planning

Visualize projections of impact, cost, and effects on racial disparities

Health Department Partnerships

The SHIELD project partners with health departments in:

  • New York City
  • Baltimore City
  • New York State

Economic Modeling

Our economic analysis assesses the affordability and cost-effectiveness of potential interventions for syphilis control:

  • Estimating costs from both healthcare and societal perspectives
  • Calculating total budget impact based on population coverage
  • Determining cost per quality-adjusted life year (QALY) gained
  • Evaluating cost per syphilis infection averted and cost per congenital syphilis case averted

"Given funding constraints in the public health landscape, effective allocation of scarce public health resources is critical to controlling the syphilis epidemic."