Background
 
Achieving 70% cervical cancer (CC) screening coverage in Mexico requires innovative approaches for improving access. The Mexican Institute of Social Security (IMSS), serving approximately 31 million women, currently relies on cytology-based opportunistic screening with only 10% coverage. To address this gap, IMSS launched the Maquilas pilot program at the U.S.–Mexico border —a workplace-based, multi-component intervention utilizing an HPV self-sampling as primary screening implemented in maquilas (manufacturing factories) and a risk-based colposcopy triage in the routine IMSS CC screening program. While the program demonstrated increased screening uptake by women, there is wide variability in the level of implementation across maquiladoras. Since program implementation and effectiveness have not yet been evaluated, reasons for this variability are unclear. Additionally, implementation strategies used were not specifically designed to address identified barriers to implementation, and their impact has not been assessed. 
 
Objectives
 
We aimed to identify factors influencing the implementation of the cervical cancer screening program in Ciudad Juárez, Mexico, to inform the adaptation and or design of the intervention and implementation strategies for national scale-up.
 
Methods
 
We conducted 30 semi-structured interviews with healthcare providers across 10 factory-based physicians' offices, 11 IMSS primary care clinics, and 2 colposcopy units, plus 6 interviews with IMSS leaders and program developers. Maquilas selection included sites with varying performance levels. Interviews explored experiences with program delivery, coordination, training, and follow-up processes. We applied thematic analysis informed by the Consolidated Framework for Implementation Research (CFIR).
 
Results
 
At maquila worksites, where HPV self-sampling kits were distributed, providers perceived the program as highly acceptable and effective for increasing screening uptake. Key facilitators included accessible educational materials, a patient-centered workplace culture, women’s trust in maquila medical services, and established collaborations between IMSS and maquilas. Major barriers were high workforce turnover, which disrupted continuity and follow-up of HPV-positive women, and perceived increases in workload in some maquilas.
 
In IMSS primary care clinics, physicians and nurses reported challenges maintaining fidelity to implementation protocols, particularly regarding training dissemination and standardized procedures in environments characterized by large staff sizes, diverse professional roles, and rotating shifts. Colposcopy units faced difficulties managing surges in referrals generated by intensive maquila campaigns and ensuring timely diagnostic follow-up, highlighting system-level capacity constraints.
 
Across all settings, mid-level leaders and operational staff demonstrated strong motivation and effective delegation skills. However, interviewees desired more participatory involvement in program design, including regular updates on progress and patient outcomes.
 
Conclusion.
This study identified critical organizational and process-related determinants shaping the implementation of workplace-based HPV self-sampling across a large public health system. Addressing workforce dynamics, clinic capacity, training infrastructures, and feedback mechanisms will be central to optimizing integration across worksites, primary care, and diagnostic services. These findings provide a roadmap for integrating workplace-based HPV self-sampling into standard cervical cancer care within Mexico's largest healthcare system, with implications for similar programs in low- and middle-income countries seeking to expand screening access through innovative delivery platforms.