The Public Health Response to Human Trafficking: A Look Back and a Step Forward

Human trafficking (eg, compulsory forced labor or commercial sex or involvement of a minor in commercial sex acts) ¹ is a public health issue that results from interconnected factors at societal, community, family, and individual levels.^2,3 Traffickers disproportionately target populations at risk of exploitation, including people who have experienced or been exposed to other forms of violence (eg, child abuse or maltreatment, interpersonal violence or sexual assault, community or gang violence) and people disconnected from stable support networks (eg, those who have run away from home or experienced homelessness, unaccompanied minors, people displaced during disasters).^4,5 Structural racism, xenophobia, gender inequality, and misogyny magnify this vulnerability. ⁶

Increasingly, public health strategies drive human trafficking research, ⁷ including investigations using sophisticated methods of prevalence estimation,^8,9 the design and validation of screening tools,^10-12 and the use of sentinel surveillance to detect trends in human trafficking. ¹³ While much research focuses on identifying risks and vulnerabilities at the individual and relationship levels,^14,15 there is an increasing focus on studying cultural factors that influence human trafficking at the societal level, including systemic racism and other beliefs and attitudes that foster the marginalization of large groups (eg, homophobia, transphobia).^16-18

Because human trafficking is a public health issue, intervention and prevention efforts must be founded on a strong evidence base and informed by affected populations, including those with lived experience, and by using an equity lens. This supplement, “The Public Health Response to Human Trafficking: A Look Back and a Step Forward,” aims to build the evidence base for human trafficking prevention and intervention and elevate the importance of strong public health responses to commercialized forms of violence. It highlights innovative strategies for human trafficking research, prevention, and service delivery, including advanced methods of prevalence estimation, use of telemental health services, and a study of racial bias and discrimination in the field. The studies in this supplement prompt additional research questions and encourage new strategies for identifying and serving those who have experienced human trafficking.

Multiple studies in this issue highlight the strengths of the public health approach to human trafficking. In their topical review, Schroeder et al ⁸ compare public health methods of estimating the prevalence of hard-to-reach populations (eg, sex workers, undocumented migrant workers) and discuss implications for human trafficking research. They acknowledge the inherent difficulties in accurately estimating the number of trafficked people regionally and globally and describe tangible (eg, lack of coordinated data systems) and methodological (eg, inconsistent definitions of key terms) challenges. They review the strengths and weaknesses of network- and venue-based approaches, including respondent-driven sampling, the network scale-up method, time–location sampling, and Vincent link tracing sampling. The authors caution that circumstances, context, and push/pull factors vary globally, and the heterogeneity of the human trafficking experience requires flexibility when choosing an appropriate method. They describe the Prevalence Reduction Innovation Forum, which seeks to assess and compare the utility of multiple prevalence estimation methods among populations of people who have experienced human trafficking.

Gallo et al ¹³ approach the challenges of identifying people impacted by human trafficking and assessing trends in exploitation by advocating for the use of an active sentinel surveillance system in which a nonrandom sample of service sites is targeted for surveillance based on frequent use by people at risk for human trafficking. They suggest that community health centers (CHCs) in the United States serve in this capacity and that routine patient screening for risk of human trafficking, combined with the use of new International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) diagnostic codes for human trafficking,^19,20 would allow monitoring of trends in the number and characteristics of trafficked people. They argue that this methodology allows for an in-depth analysis of case information and requires special training of relatively few staff members, because sites are limited in number and resources may be concentrated. The authors review the infrastructure needed for CHCs to implement a successful surveillance system for human trafficking, including the relatively new requirement for CHC providers to enter ICD-10-CM codes for human trafficking into the Health Resources & Services Administration’s CHC Universal Data System (UDS). Gallo et al also discuss the potential challenges in creating a sentinel surveillance system within CHCs, including restrictions on the staff eligible to report in the UDS and concerns about confidentiality and privacy. The authors make recommendations for meeting these challenges, including expanding the pool of CHC providers eligible to enter data in the UDS, improving training on and awareness of human trafficking, and implementing trauma-informed approaches to screening for exploitation.

Additional articles in this supplement use a public health framework to examine the characteristics of human trafficking and current ways of understanding the phenomenon. Barnert et al ²¹ describe the relationships between commercial sexual exploitation during adolescence and health during adolescence and adulthood by using nationally representative data from the National Longitudinal Study of Adolescent to Adult Health. Cook et al ²² explore racial bias and discrimination in domestic sex trafficking of minors through the use of public health critical race praxis, an extension of critical race theory. The authors address 3 focus areas of public health critical race praxis as they relate to domestic sex trafficking of minors involving Black girls, including contemporary racialization, knowledge production and conceptualization, and measurement. A scoping review by Hainaut et al ²³ identified human trafficking screening tools that are used in health care settings and determined which tools have been validated. The articles in this supplement provide insight into the current evidence base supporting antitrafficking efforts and suggest innovations to advance the field.

Looking forward, we must acknowledge that public health research on human trafficking is still in a formative stage of development, a foundational period of knowledge building sometimes characterized by the hopeful phrase per aspera ad astra (“through difficulties to the stars”). This phase of scholarship is strongly affected by history, politics, international trends, and/or other sociocultural, legal, and environmental conditions that dictate and influence research priorities, funding, and definitions. The current state of the science reflects a fragmentary, dynamic, global awakening to the problem of human trafficking. There is a recognized need and unmet challenge to generate and disseminate knowledge beyond localized agency and intrajurisdictional boundaries and to provide data that facilitate accountability and performance improvements across systems and sectors.^24-26 The articles in this supplement reflect these contemporary realities.

Valid criticisms exist regarding the scope of current trafficking research. First, most research has focused on sex trafficking despite expert warnings that labor trafficking may be underrepresented in prevalence estimates.^27-30 Forced labor accounts for a substantial proportion of identified cases of human trafficking globally and may be rising (34% in 2016, 38% in 2018). ²⁷ In fiscal year 2020, 81% of adult foreign nationals and 74% of child foreign nationals certified by the US Department of Health and Human Services had experiences of labor trafficking. ²⁸ The lack of research focus on labor trafficking can be seen as a perpetuation of historical inequities seen throughout the antitrafficking history in the United States related to the devaluing of people of color, including immigrants of color. The US Department of State’s 2021 Trafficking in Persons report underlines a “continued lack of progress and sustained effort to address labor trafficking . . . including in efforts to identify [labor trafficking] victims.” ²⁸ Second, trafficking research has been further constrained by its attention to the experiences of women and girls, ³⁰ with minimal research dedicated to individuals of other genders, ³¹ and a paucity of data collection on transgender and nonbinary populations. The 2020 United Nations Global Report on Trafficking in Persons ²⁷ documents an increasing proportion of male victims (28% in 2016 vs 35% in 2018), and evidence suggests an increased risk for exploitation among those identifying as lesbian, gay, bisexual, transgender, queer, questioning, 2-spirit, or other (LGBTQ2S+).^17,32,33

Based on global 2018 data involving people known to have been victimized, women were more likely than men to be trafficked for sexual exploitation, and men were more likely to be trafficked for forced labor; however, considerable variability exists by sex. ²⁷ Unfortunately, a paucity of studies disaggregate data by sex and gender, compare characteristics of sex versus labor trafficking, and examine the interaction of sex and labor trafficking experiences and outcomes. This research is especially important as we consider that putative assumptions made about sex trafficking (eg, false perceptions of victims as only female and perpetrators as only male) cannot be generalized to conditions of forced labor. As research investigations expand in scope and depth, a developmental transformation should occur in how human trafficking is detected, understood, and addressed.

Many studies that appear in the literature, including those in this supplement, focus on surveillance and screening, describe conceptual frameworks for understanding the human trafficking experience, and examine how individuals and systems of care are responding to human trafficking. The methodologies used in current and past trafficking studies tend to be based on population or convenience samples that are informed by disciplinary frameworks from social science, criminal justice, medicine, and epidemiology. The articles included in this supplement reflect this trend. These studies are foundational elements for a new generation of research that could apply randomized controlled trial designs or alternatives such as regression point displacement, regression discontinuity, and propensity score–matching methodologies ³⁴ to test the efficacy and effectiveness of public health interventions that are individual, community, and systems focused. The development of testable protocols could have the added public health benefit of operationalizing the delegated functions, case management, outreach strategies, and maintenance components of these practice algorithms. Intervention programs can be advanced by the application of rigorous research protocols, including longitudinal designs, to determine whether short-term outcomes can be sustained.

An expansion of the scope of these investigations beyond effectiveness outcomes to include implementation process variables is also necessary to catalogue the drivers of successful and sustainable evidence-based approaches as they emerge. Implementation science is “the scientific inquiry into questions concerning implementation, the act of carrying an intention into effect, which in health research can be policies, programmes, or individual practices (collectively called interventions).” ³⁵ Implementation-focused research helps advance a field beyond the exploration and description phase and allows empiricism to influence policy and practice with adequacy, plausibility, and probability.^35-38 Little evidence indicates that implementation science frameworks or methodologies have been applied formally to the field of human trafficking research to date, making it an ideal time to use this approach to propel the field into the next stage of its developmental trajectory.

As we look forward to the next generation of antitrafficking public health research, we have an opportunity and responsibility to reflect on and learn from the past. US public health research has a history of contributing to inequities. ³⁹ Our antitrafficking response, including research funding mechanisms, trafficking data, and the interest of researchers, has been shaped by the forces of structural racism and xenophobia.^6,29,40 As a team of co-editors who are White, cisgender, US-born women in academia without a lived experience of trafficking, we acknowledge the inherent privilege and biases we bring to our analysis of the state of the public health trafficking research.

Bearing this in mind, we make the following recom-mendations.

1. Future research should be based on equity-grounded theories addressing trauma, interpersonal violence, and social determinants of health. A thoughtful approach should be taken to “hypotheses, study design, measured variables, and unmeasured covariates likely to be important, as well as potential confounders and possibilities of selection bias.” ⁴¹

2. Research should be designed and implemented with the input of affected communities, including those with lived experiences of trafficking, using established community-based participatory research engagement strategies and ethics.

3. Balance measures, used to assess for unintended consequences, may be developed in partnership with people affected by trafficking-specific interventions, such as adults engaged in commercial sex and undocumented migrant workers. Every effort should be made to center the voices of those at the margins of US society, including, but not limited to, labor-trafficked people; American Indian/Alaska Native, Native Hawaiian/Other Pacific Islander, Black, and indigenous people, and people of color; unaccompanied migrant minors; men and boys; and people who identify as LGBTQ2S+.

4. Research agendas should be shaped by diverse audiences including academic researchers, public health practitioners, policy makers, and global, national, and community-based advocacy organizations of affected populations, including those with lived experience.

5. All public health antitrafficking research should be critically appraised for:

   1. theoretical frameworks used/not used
   2. populations studied and excluded
   3. rigor of methodologies
   4. candidness and clarity of translation of findings, including the limitations of its generalizability
   5. contextualization in the broader societal and historical context.

Public health research, if conducted rigorously and grounded in equity, has the power to change the systems and structures that allow human trafficking to persist and propagate. We need to reflect on limitations of prior research and learn from those with lived experience of human trafficking to shape the future of public health anti-trafficking research.