From outbreak to opportunity: Leveraging Lassa fever trends from 2018 to 2025 to strengthen trial site preparedness and vaccine acceptance in Ebonyi State, Nigeria

Abstract

Introduction Lassa fever remains a major public health threat in West Africa, with Nigeria bearing a substantial burden. Ebonyi State, Nigeria, is a recognised hotspot, and Alex Ekwueme Federal University Teaching Hospital Abakaliki (AEFUTHA) serves as the region’s principal treatment centre and a designated site for a Phase 2b Lassa fever vaccine clinical trial. This study aimed to analyze trends in confirmed Lassa fever cases to inform vaccine trial preparedness, optimize recruitment strategies, and support vaccine acceptance efforts in endemic settings. Methods A retrospective descriptive study was conducted using data on confirmed Lassa fever cases reported in Ebonyi State from 2018 to April 2025. Data were sourced from the Ebonyi State Ministry of Health and AEFUTHA’s Lassa treatment register. All 416 confirmed cases were analyzed using IBM-SPSS version 25 to assess temporal trends, age and sex distribution, seasonal patterns, geographic origin, survival rate and case fatality rate (CFR). Results Males accounted for 56.5% of 416 confirmed cases. The most affected age groups were 21–30 years (24.5%) and 31–40 years (25.2%). The overall CFR was 38.5%, peaking in 2023 (56.9%) and 2025 (57.9%). Seasonally, 83.7% of cases occurred between January and March. Geographically, 96.2% were from Ebonyi State, with a small number of referrals from neighbouring states. The annual incidence peaked in 2020, with 90 cases (21.6%), followed by a decline in subsequent years. Conclusion This eight-year trend analysis demonstrates the predictable epidemiological pattern of Lassa fever in Ebonyi State and provides critical insights for planning vaccine trial logistics, recruitment timing, and community engagement. The study enhances the trial site’s readiness for vaccine trials and offers a practical evidence base for advancing equitable Lassa fever vaccine deployment in endemic West African regions.