Safety first, science second: Healthcare workers' conditional trust and willingness to participate in Lassa fever vaccine trials in Nigeria

BACKGROUND: Lassa fever poses a persistent occupational risk to healthcare workers (HCWs) in Nigeria. While HCWs are pivotal to vaccine trial success, their decision-making in settings shaped by historical research controversies remains poorly understood. This study explored the conditions under which HCWs at Aminu Kano Teaching Hospital (AKTH), northern Nigeria, considered participation in Lassa fever vaccine trials acceptable. METHODS: We conducted a descriptive qualitative study using semi-structured in-depth interviews with 20 physicians, nurses, and midwives at AKTH between September and October 2025. Participants were recruited through purposive and snowball sampling. Interviews were audio-recorded, transcribed verbatim, and analysed using reflexive thematic analysis. Reporting followed the Consolidated Criteria for Reporting Qualitative Research (COREQ). RESULTS: HCWs did not frame participation as a simple decision to accept or refuse vaccine trials. Instead, they described a pattern of cautious conditionality, whereby willingness depended on explicit safety, ethical, and institutional conditions being met. Decisions were shaped by perceptions of occupational risk, scientific uncertainty, professional responsibility, institutional trust, and the enduring influence of the 1996 Pfizer meningitis trial in Kano. Transparent safety information, robust informed consent, credible ethical oversight, fair compensation for research-related harm, and institutional accountability emerged as essential conditions for participation. CONCLUSIONS: Within the distinctive historical and institutional context of AKTH, HCWs approached Lassa fever vaccine trials as ethically discerning evaluators rather than passive research participants. These findings highlight actionable features for the ethical design and implementation of Lassa fever vaccine trials in endemic settings.