The ENABLE 1.5 Lassa Research Programme — funded by the Coalition for Epidemic Preparedness Innovations (CEPI) — is operating in Liberia, Nigeria, and Sierra Leone from late 2024 to mid-2026. With a prospective cohort of 5,000 participants (at least 1,000 per site), the study will monitor individuals for a year to capture fresh insights into Lassa virus incidence, malaria co-infections, and long-term complications such as 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. That earlier research revealed an overall Lassa virus seroprevalence of about 30%, with Edo State, Nigeria, recording the highest incidence — 1.9 cases per 1,000 people — during surveillance. It also found that children are just as vulnerable as adults, and that mild cases often go undetected.
CEPI says ENABLE 1.5 will use RT-PCR testing to confirm symptomatic infections, quantify malaria co-infections in Lassa patients, and assess rates of sensorineural hearing loss in survivors. The data will inform vaccine trial design and public health strategies, particularly in high-burden communities.
Beyond medical testing, researchers will examine how local populations perceive Lassa vaccination and whether they would participate in future clinical trials. To improve acceptance, the study is incorporating participatory approaches — engaging community health workers, survivors, and local advocates to build trust. Outreach will include education on rodent control, environmental sanitation, and mosquito net use, recognising that malaria and Lassa fever can co-exist in the same populations.
Communities previously involved in ENABLE 1.0 will receive updates on earlier findings, a move aimed at transparency and maintaining relationships. Participants will undergo regular check-ups, blood tests, and hearing assessments. Any suspected cases will be screened for both Lassa and malaria, with confirmed cases referred promptly to treatment centres. Survivors will be followed over months to track recovery, identify delayed complications, and understand the socioeconomic impact of the disease.
Lassa fever — an acute viral haemorrhagic illness spread mainly by contact with infected rodent urine or droppings — can cause severe disease, including multi-organ failure. Fatality rates in severe cases can reach 70%. While traditionally peaking in the dry season, recent patterns suggest year-round transmission, potentially influenced by climate change, urbanisation, and shifting environmental factors.
CEPI believes ENABLE 1.5 will generate the evidence needed to move toward late-stage vaccine trials and stronger outbreak preparedness. “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,” the agency said.
The findings are expected to shape the region’s long-term strategy against a disease that has persisted for decades, ensuring that when vaccines become available, they will be embraced and deliver real public health impact.