Why Oxford’s Lassa Vaccine Trial Matters for Millions at Risk in West Africa

For decades, Lassa fever has haunted West Africa as a deadly disease, causing yearly spikes in illness, deaths, and fear. In Nigeria alone, over 900 confirmed cases and about 170 deaths have been recorded this year. Against this backdrop, the Oxford Vaccine Group’s new Lassa vaccine trial, backed by CEPI, offers a rare glimmer of hope for millions at risk, writes Sunday Ehigiator

For millions of people across West Africa, Lassa fever is not an abstract health threat discussed in policy papers or laboratories; it is a recurring reality that returns with unsettling predictability.

Each year, as the dry season peaks, hospitals in Nigeria and neighbouring countries begin to see a rise in cases. Healthcare workers steel themselves for difficult months ahead, and communities in rural areas confront a disease that has long been overshadowed by global health priorities.

The recent vaccination of the first human volunteer in a Lassa fever vaccine trial by the Oxford Vaccine Group marks a quiet but potentially transformative moment in this long struggle.

Funded by the Coalition for Epidemic Preparedness Innovations (CEPI), the trial represents the first time a Lassa vaccine candidate has been tested in humans, offering hope to a region that has lived with the virus for more than half a century without a licensed vaccine or targeted treatment.

A Critical First Step

For CEPI, the trial is far more than a scientific milestone. CEPI’s Lassa Disease Programme Lead, Dr Katrin Ramsauer, describes it as a turning point built on years of groundwork.

“Lassa fever is endemic in West Africa and poses a persistent public health threat, yet there is no licensed vaccine,” she explains.

“The start of this first-in-human trial led by the Oxford Vaccine Group is a critical step. We need several vaccine candidates moving forward at the same time to ensure we eventually have a licensed and accessible vaccine for the region.” According to Ramsauer, Oxford’s work strengthens a growing global pipeline that includes other candidates already in later-stage trials, including in Nigeria. “This is about increasing the chances of success,” she says. “No single effort can carry the weight alone.”

Built on Proven Vaccine Science

At the centre of the trial is the ‘ChAdOx1 vaccine’ platform, the same technology used to develop the Oxford/AstraZeneca COVID-19 vaccine. The Chief Investigator of the VITAL01 Lassa vaccine trial and Professor of Infection and Vaccinology at the University of Oxford, Professor Maheshi Ramasamy, says the decision to use the platform was driven by experience and evidence.

“This vaccine uses a harmless chimpanzee adenovirus that has been modified to carry genetic material from the Lassa virus. It does not contain the whole virus, but it trains the immune system to recognise and respond to Lassa.” The platform’s track record, she notes, is reassuring. “More than two billion doses of COVID-19 vaccines using this technology have been given worldwide, so we understand its safety, how it stimulates the immune system, and how it can be manufactured at scale.”

According to her, that familiarity allows scientists to focus on the unique challenges of Lassa fever itself, “particularly the fact that researchers still do not fully understand what protective immunity against the virus looks like.”

Why First-in-Human Trials Matter

Administering the first dose of a vaccine to a human volunteer is a critical and meticulously controlled moment in medical research, marking the transition from laboratory and animal studies to human testing. Prof. Ramasamy stresses that Phase 1 trials are primarily about safety, not proving efficacy in the broader population.

“Before reaching this stage, the vaccine underwent extensive testing in animals, including mice, guinea pigs, and non-human primates, to evaluate safety and the ability to stimulate an immune response.

“When we move into human trials, we proceed very cautiously. We start with one participant at a time, monitoring them closely for any side effects, local reactions at the injection site, or changes in blood markers. “Participants are observed for both immediate and long-term responses. We follow volunteers for up to a year, conducting regular blood tests to assess liver, kidney, and bone marrow function, as well as detailed immunological studies.

“Phase 1 studies are deliberately small and methodical. Without this careful first step, we cannot ethically or safely progress to larger trials in the regions where Lassa fever is endemic.

“The Oxford trial currently involves 31 healthy volunteers in the UK, representing a diverse cohort aged 18 to 55.

“A second Phase 1 trial is planned in Ghana early next year, bringing research closer to affected communities and providing essential data on how the vaccine performs in populations with potential exposure to Lassa fever. “Conducting trials in endemic regions is crucial,” Ramasamy adds. “It allows us to evaluate safety in a population that may have prior exposure to the virus and builds the groundwork for eventual Phase 2 and Phase 3 studies that can determine effectiveness.” The first-in-human dose is thus both symbolic and practical; a scientific milestone that demonstrates years of rigorous preparation, while laying the foundation for future trials aimed at protecting millions across West Africa.

Beyond a Single Trial

The Oxford Lassa vaccine trial is not simply a standalone scientific experiment. According to Dr Ramsauer, it is part of a deliberate, multi-layered strategy to build a sustainable ecosystem for disease control in West Africa, extending far beyond the immediate goal of producing a vaccine. “Funding vaccines alone is not enough. We are investing in the broader ecosystem around vaccine development,” she explains.

CEPI’s support has strengthened both clinical and diagnostic capacity at key treatment centres, such as the Irrua Specialist Teaching Hospital (ISTH) in Edo State, long recognised for its expertise in managing Lassa fever, and Abubakar Tafawa Balewa Teaching Hospital (ATBTH) in Bauchi State.

These hospitals have benefited from upgraded molecular-diagnostic laboratories capable of processing hundreds of suspected Lassa cases using RT-PCR technology, bringing greater precision to diagnosis and improving patient care. Such improvements form the essential foundations for both effective outbreak response and future clinical trials.

Beyond Nigeria, CEPI has also supported clinical-trial readiness across multiple countries in West Africa. Through initiatives such as the UNVEIL project, three Nigerian hospitals, ISTH, ATBTH, and Jos University Teaching Hospital, serve as frontline clinical sites alongside partner sites in Sierra Leone.

These studies aim to identify immune correlates of protection, biological markers that indicate immunity to Lassa, which could allow future vaccines to be evaluated more quickly and accelerate deployment across affected communities.

Equally critical is the investment in human resources. Recent training initiatives in Ebonyi, Bauchi, and Benue states have equipped over 230 health workers, including doctors, nurses, community health officers, and surveillance staff, with knowledge and skills in Lassa fever case management, infection prevention, and outbreak response.

These investments ensure that the human and institutional capacity exists not only to support current trials but to respond effectively to future epidemics. As Professor Ramasamy puts it, “Clinical trial capacity is not just for one disease; once these systems are in place, they can be adapted for other outbreaks.”

In addition, CEPI’s work supports regulatory and research infrastructure, including ethical oversight, data management, and safety monitoring. These systems ensure that once a vaccine is proven safe and effective, it can be licensed and deployed rapidly, bridging the gap between scientific success and real-world impact.

Taken together, the Oxford Lassa vaccine trial may be the spark, but the investments in laboratories, trained personnel, regulatory pathways, and surveillance networks represent the pillars of a stronger, more resilient health system.

If successful, this infrastructure will provide benefits far beyond the vaccine itself, potentially transforming West Africa’s ability to detect, respond to, and prevent not only Lassa fever but also future epidemic threats.

Preparing Communities, Not Just Clinics

Across Nigeria, the burden of Lassa fever is concentrated in a handful of high‑risk states; a reality that underscores why community engagement matters just as much as clinical readiness.

According to recent data from the Nigeria Centre for Disease Control and Prevention (NCDC), five states, Ondo State, Bauchi State, Edo State, Taraba State and Ebonyi State, accounted for about 91 per cent of all confirmed Lassa cases in 2025.

This concentration has driven targeted community outreach efforts. In Benue State, for example, the World Health Organisation (WHO), in collaboration with the state’s Ministry of Health, recently launched sensitisation campaigns across 45 high-risk communities.

Activities included market and worship‑place outreach, public talks, and distribution of educational materials, all aimed at improving early detection and promoting preventive practices.

For Dr Ramsauer, this kind of community-level engagement is indispensable. “We cannot arrive with a vaccine in a few years and expect automatic acceptance. Communities need to be part of the journey from the beginning, understanding the disease, how it spreads, and how vaccines work to protect their families and neighbours.”

CEPI’s epidemiological studies, conducted in Nigeria and other affected countries, are therefore designed not just to collect data, but also to serve as channels for education and trust-building.

Ramsauer explains: “These studies are not just about numbers; they are about conversations. We engage with local leaders, households, and community groups. We answer their questions, correct misconceptions, and gradually build confidence in public health interventions.”

This groundwork is especially important because Lassa fever often begins with symptoms easily mistaken for malaria or other common illnesses. In such situations, delay in seeking care or reliance on traditional remedies can worsen outcomes and fuel spread.

Bringing communities into the fold early helps ensure better recognition of symptoms, quicker response, and greater acceptance of prevention strategies.

Professor Ramasamy, in her remarks, emphasised that acceptance will depend as much on trust as on science. “We are not just developing a vaccine in a lab. We are talking about people’s lives, their homes, their communities. For success, there needs to be clarity, respect, and transparent communication long before the first dose is administered.”

In practical terms, especially in states like Ondo, Bauchi, and Edo, which remain the epicentres, this means combining health‑system strengthening with local dialogue, environmental sanitation (to reduce rodent contact), transparent information sharing, and culturally sensitive mobilisation.

If those elements come together, experts say, a Lassa vaccine can become more than a medical tool; it can become a turning point in community resilience and regional disease control.

Lessons from COVID-19

The COVID-19 pandemic looms large over the Lassa vaccine effort. For Ramasamy, it reshaped how scientists think about preparedness.

“COVID-19 showed us that you can move quickly without cutting corners if systems are in place. We learned how to run development stages in parallel, how to scale manufacturing, and how to monitor safety at speed.

“Those lessons are now being applied to Lassa fever, a disease that may not threaten the whole world at once but places a heavy and recurring burden on West Africa. Preparedness is not just for global pandemics, it’s also for endemic diseases that quietly devastate communities year after year.”

What Is at Stake for West Africa

The potential benefits of a successful Lassa vaccine extend far beyond individual protection. Nigeria alone records an estimated 24,000 hospital admissions related to Lassa fever annually, while thousands die across the region. Healthcare workers often bear the brunt of exposure, leading to fear, absenteeism, and strained health systems during peak seasons.

According to Ramsauer, “A vaccine could stabilise healthcare services. If healthcare workers are protected, hospitals can function properly during outbreaks. Families are spared the long-term illness, stigma, and economic hardship that come with severe cases.”

Adding her voice, Prof. Ramasamy, noted that “Vaccinating frontline workers is just the first step. Over time, broader immunisation could reduce maternal deaths; pregnant women are among the most vulnerable, and protect children and rural populations where the disease is most prevalent.”

Ramsauer adds that the vaccine could also strengthen communities’ confidence in healthcare systems. “When people see that vaccines work and are safe, it builds trust. Communities are more likely to participate in other prevention efforts, and that ripple effect strengthens overall outbreak preparedness.”

While Ramasamy notes the economic benefits: “Every Lassa season, affected individuals are unable to work for weeks, sometimes months. Families lose income, and local economies suffer. A vaccine can prevent these disruptions, keeping communities healthier and more resilient.”

Both experts emphasise that this is not just about immediate protection but long-term regional resilience. “The goal,” Ramsauer says, “is to ensure that West Africa can respond to Lassa and other epidemic-prone diseases effectively, with fewer lives lost and health systems under less strain.”

A Measured Hope

Both Professor Ramasamy and Dr Ramsauer were careful to temper expectations. Even with promising early results, a licensed Lassa vaccine is not an immediate reality.

“We anticipate that, if all goes well, it could take five to seven years before a vaccine is fully licensed and widely available,” Ramsauer cautions. “But what this trial does represent is a critical forward movement in the fight against a disease that has been largely neglected for decades.”

Ramasamy adds that the careful, stepwise approach is deliberate. “Phase 1 trials are about ensuring safety first, and understanding how the immune system responds. This foundation is essential before moving into larger trials that can truly assess protection in the populations most at risk.”

For the millions living in Lassa-endemic areas, that progression, though measured, is itself a milestone.

Annual outbreaks in Nigeria alone account for hundreds of deaths and thousands of hospitalisations, placing immense strain on healthcare systems and communities.

Ramsauer highlights the significance of a locally grounded approach: “We are not just developing a vaccine in isolation; we are working with regional partners, health authorities, and communities to ensure that once the vaccine is ready, it can be adopted effectively and equitably.”

The experts emphasise that this trial, and the broader strategy surrounding it, signal a turning point. After decades of scientific oversight and limited investment, Lassa fever has reached a stage where credible, coordinated, and regionally informed solutions are emerging.

Each carefully monitored dose is a tangible step toward protecting vulnerable populations, building trust in vaccines, and strengthening the capacity to respond to future outbreaks. “This trial does not mean we are finished,” Ramsauer says. “It means we are moving forward with purpose; and for communities living under the constant threat of Lassa fever, that is reason enough for hope.”