The ENABLE 1.5 Lassa Research Programme is underway across West Africa to close critical knowledge gaps on Lassa fever, its link to malaria, and community readiness for upcoming vaccines.
Funded by the Coalition for Epidemic Preparedness Innovations (CEPI), the multi-country study began in late 2024 and will continue until mid-2026, covering Liberia, Nigeria, and Sierra Leone. It aims to generate significant scientific data and improve public health strategies.
The prospective cohort study has enrolled 5,000 participants — at least 1,000 at each site — who will be monitored for a year to assess Lassa virus incidence, malaria co-infection, and potential long-term effects such as permanent hearing loss.
This phase builds on ENABLE 1.0 (2021–2023), which involved over 23,000 participants in Benin, Guinea, Liberia, Nigeria, and Sierra Leone. The earlier study provided key insights into Lassa virus exposure and distribution patterns, recording an average seroprevalence of 30 percent. Edo State, Nigeria, had the highest incidence rate, with 1.9 cases per 1,000 people. The findings also confirmed that children are just as vulnerable as adults.
Researchers note that mild cases often go undetected, and malaria co-infection in Lassa patients remains insufficiently studied. ENABLE 1.5 will measure symptomatic infection rates using RT-PCR testing, examine malaria co-infection levels, and evaluate the occurrence of sensorineural hearing loss among survivors. The data will help guide vaccine trials and shape public health interventions.
The programme also explores community attitudes toward Lassa vaccination and participation in future clinical trials. Using participatory methods, the team aims to boost vaccine acceptance and trust in high-risk populations. Efforts to reduce participant dropout include engaging community health workers and Lassa fever survivors as advocates, as well as promoting rodent control, environmental sanitation, and the use of insecticide-treated mosquito nets.
Communities from the first phase will receive updates on past results, ensuring transparency and reinforcing local partnerships. Random household selection in Lassa hotspots will ensure balanced representation across five age groups.
Participants will receive regular check-ups, blood tests, and hearing assessments. Suspected cases will be tested for both Lassa fever and malaria, with confirmed cases referred to treatment centres according to national guidelines. Survivors will be followed for months to monitor recovery, identify delayed complications, and document the long-term health and socioeconomic impacts of the disease.
Lassa fever is an acute viral haemorrhagic illness mainly transmitted through contact with rodent urine or droppings. Severe cases can lead to multi-organ failure, with fatality rates as high as 70 percent. While the disease typically peaks during the dry season, recent trends suggest year-round transmission in Nigeria, Liberia, and Sierra Leone, possibly driven by climate change, urbanisation, and other environmental factors.
According to CEPI, the ENABLE 1.5 study will provide the robust evidence needed for late-stage vaccine trials, guide vaccine delivery strategies, and strengthen regional outbreak preparedness for Lassa fever and related health threats.
By understanding the full burden of the disease — including mild and paediatric cases — health authorities will be better equipped to target interventions and prepare for the rollout of future vaccines. The findings are expected to shape West Africa’s long-term response to a virus that has persisted for decades, ensuring communities are ready to embrace and benefit from new prevention tools when they become available.