A candidate vaccine aimed at combating Lassa fever has initiated its inaugural human trials in the United Kingdom, creating optimism for enhanced prevention of a disease that consistently leads to annual outbreaks in Nigeria and West Africa.
This advancement was revealed during an exclusive interview conducted with PREMIUM TIMES alongside global health officials and researchers involved in the creation of the Lassa fever vaccine.
The vaccine is being developed by scientists at the University of Oxford, a renowned research institution in the UK, supported by the Coalition for Epidemic Preparedness Innovations (CEPI), an organization dedicated to funding vaccine development for diseases at risk of causing epidemics.
The ongoing trial represents a Phase one study intended to evaluate the safety of the vaccine among healthy adult volunteers. Should this phase prove successful, the next steps will include expanding trials into Africa, particularly Nigeria, which is one of the countries with the highest incidences of the disease.
A Long-standing Public Health Concern
Lassa fever, a viral hemorrhagic illness, is primarily found in parts of West Africa. Nigeria consistently has the highest reported cases annually, with outbreaks imposing considerable pressure on the nation’s public health infrastructure.
Despite its recognition over fifty years ago, no licensed vaccine has been available for the disease.
Katrin Ramsauer, who leads the Lassa programme at CEPI, emphasized that the slow progress in vaccine development is largely due to Lassa fever mostly impacting low- and middle-income nations, which diminishes attractiveness for pharmaceutical industries.
“Although Lassa fever was first identified in 1969, survivors frequently endure lasting complications such as auditory impairment and neurological issues,” stated Ms. Ramsauer, noting that the actual burden of the disease is likely underestimated.
CEPI was established following the Ebola outbreak from 2014 to 2016 to bridge this gap by funding vaccine initiatives for diseases that have a significant public health effect yet lack commercial viability.
Reasons for Initial Trials Outside Nigeria
When questioned about the rationale behind not initiating trials in Nigeria, Ms. Ramsauer explained that early-stage clinical trials are generally carried out in regions with established research capabilities to maximize safety and efficacy. She mentioned that Nigeria is concurrently hosting other Lassa fever vaccine studies, including a Phase two trial backed by CEPI from another developer, affirming its pivotal role in future plans.
“Nigeria is entirely prepared for clinical trials,” she remarked, highlighting CEPI's investment in enhancing the country's clinical trial capacity to facilitate vaccine research.
While the candidate developed in Oxford starts its Phase one trials in the UK, it is anticipated to proceed to Ghana for supplementary early-stage assessments before moving into later phases within Nigeria and other West African countries.
Fostering Community Trust and Vaccine Acceptance
Oyeronke Oyebanji, who heads CEPI’s engagement concerning Lassa fever in West Africa, noted how the organization collaborates closely with regional governments to secure community acceptance and ensure equitable vaccine access in the future.
Together with the West African Health Organisation, CEPI founded the Lassa Fever Coalition, which comprises Nigeria, Liberia, Sierra Leone, Guinea, and the Benin Republic. Ms. Oyebanji explained that the coalition creates a collaborative environment for governments, scientists, and policymakers to coordinate on vaccine development, deployment, pricing, and availability.
CEPI is also funding social science research in Nigeria, Liberia, and Sierra Leone to gain deeper insights into vaccine hesitance, the willingness to join clinical trials, and community perspectives on Lassa fever vaccines.
“We are starting early in this process because trust and acceptance are essential, and the situational context can evolve over time,” she emphasized.
Progress of Early Trials
Maheshi Ramasamy, an infectious disease specialist at the University of Oxford, reported that six healthy participants aged 18 to 50 have also received the experimental vaccine in the Phase 1 trial thus far. She described the vaccine as being built on the ChAdOx1 platform, similar to the viral vector technology used in the globally administered Oxford–AstraZeneca COVID-19 vaccine.
All six trial participants are doing well, with no recorded severe adverse effects, and any reported side effects have been mild and temporary, including brief arm discomfort, fatigue, and headaches resembling typical reactions to regular vaccines.
The trial team plans to enroll an additional 25 participants in the UK and approximately 50 in Ghana before advancing to Phase 2 trials, expected to involve Nigeria.
It is essential to note that this vaccine serves as a preventive measure rather than a treatment for those already infected with the virus.
In light of the pandemic experiences, having multiple vaccine candidates is crucial to ensuring resilience in supply and production.
“Having various effective vaccines allows us to respond more swiftly and protect diverse populations during outbreaks,” she stated.
Lassa Fever's Impact in Nigeria
Lassa fever, a rodent-transmitted viral illness, predominantly transmits to humans through contaminated food, water, or household items, and can also spread from person to person through contact with infected bodily fluids.
The condition typically starts with vague symptoms like fever and weakness, potentially delaying medical attention but can escalate to severe health complications, including bleeding, respiratory distress, and organ failure if treatment is tardy.
In Nigeria, Lassa fever remains a continual public health threat.
As of epidemiological week 51 of 2025, the country documented 206 fatalities from Lassa fever, according to the Nigeria Centre for Disease Control and Prevention (NCDC). The NCDC reported that the case fatality rate escalated to 18.4 percent, up from the previous year's 16.4 percent, despite a decline in confirmed cases during the stated period.
During the week from December 15 to 21, 2025, Nigeria documented 21 new confirmed cases across seven states, including Bauchi, Ondo, Taraba, Edo, Kogi, Ebonyi, and Plateau, a decrease from 28 cases in the preceding week. However, within these confirmed cases, five deaths were reported, leading to a weekly case fatality rate of 23.8 percent.
Cumulatively, the nation recorded 1,119 confirmed cases, nine probable cases, and 9,270 suspected cases from 21 states and 105 local government areas in 2025.
While this marks a reduction compared to 2024, where 1,237 confirmed cases and 203 deaths were reported, the NCDC pointed out that the rise in fatalities is predominantly attributable to delayed presentations at health facilities.
Ondo, Bauchi, Edo, and Taraba accounted for over 88 percent of confirmed cases in 2025, with Ondo being responsible for roughly 35 percent. The NCDC cited factors such as delayed health-seeking behavior, high treatment expenses, inadequate environmental sanitation, and low awareness in high-burden communities as major contributors to the increasing fatality rate.
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