The ENABLE 1.5 Lassa Research Programme is continuing in West Africa to address gaps in knowledge about Lassa fever, its link with malaria, and community readiness for forthcoming vaccines.
The study, funded by the Coalition for Epidemic Preparedness Innovations (CEPI), was made available to newsmen on Sunday.
The study began in late 2024 and will run until mid-2026 across Liberia, Nigeria and Sierra Leone, with significant scientific and public health objectives.
The prospective cohort study has recruited 5,000 participants at least 1,000 per site who will be closely monitored for a year to measure Lassa virus incidence, malaria co-infection, and long-term complications, including permanent hearing loss.
This phase builds on ENABLE 1.0 (2021–2023), which enrolled more than 23,000 participants in Benin, Guinea, Liberia, Nigeria and Sierra Leone, providing key data on Lassa virus exposure and distribution patterns.
The earlier phase recorded an overall Lassa virus seroprevalence of about 30 per cent, with Edo State, Nigeria, reporting the highest incidence rate 1.9 cases per 1,000 persons according to surveillance findings. The study also found that children are as vulnerable to Lassa fever as adults.
“Mild cases are often missed, while malaria co-infection rates in Lassa patients remain poorly studied, necessitating targeted data gathering and analysis. ENABLE 1.5 will determine symptomatic infection rates confirmed by RT-PCR testing, measure malaria co-infection among Lassa patients, and assess sensorineural hearing loss incidence in survivors to inform vaccine trials and health interventions,” it said.
The study will also evaluate community perceptions of Lassa vaccination and willingness to participate in future clinical trials, using participatory approaches to improve acceptance and build trust in targeted populations.
To reduce participant dropout, researchers will involve community health workers and survivors as advocates, alongside sensitisation campaigns on rodent control, environmental sanitation, and insecticide-treated mosquito net usage in high-risk communities.
Communities from ENABLE 1.0 will receive updates on past findings to ensure transparency and strengthen local relationships, while random household selection in Lassa hotspots will ensure balanced representation across five age categories.
Participants will undergo regular check-ups, blood tests, and hearing assessments. Suspected cases will be tested for both diseases, and confirmed cases referred promptly to treatment centres in line with national health guidelines. Survivors will be followed for months to monitor recovery progress, detect delayed complications, and collect information on the long-term health and socio-economic impacts of the disease.
Lassa fever is an acute viral haemorrhagic illness mainly spread through contact with urine or droppings of infected rodents. Severe cases can cause multi-organ failure, with fatality rates reaching 70 per cent.
Although historically peaking during the dry season, recent trends suggest year-round transmission in Nigeria, Liberia and Sierra Leone, potentially driven by climate change, urbanisation and other evolving socio-environmental factors influencing disease patterns.
CEPI said ENABLE 1.5 will generate robust evidence for late-stage vaccine trials, inform delivery strategies, and strengthen regional outbreak preparedness and response for Lassa fever and related health challenges.
“By understanding the true burden, including mild cases and paediatric infections, we can better target interventions and prepare effectively for the introduction of future vaccines,” CEPI said.
The findings are expected to shape West Africa’s response to a disease that has persisted for decades, ensuring that when vaccines become available, communities will be ready to accept and benefit from them.
