First Lassa Fever Vaccine Enters Human Trials in UK

After more than 50 years without a vaccine, a disease that kills hundreds of people in West Africa every year finally has hope on the horizon.

University of Oxford researchers have begun the first human trials of a Lassa fever vaccine in the United Kingdom, with plans to expand testing to Ghana and Nigeria in the coming months. The viral disease has plagued West Africa since 1969, with Nigeria bearing the heaviest burden of any country worldwide.

So far, all six healthy volunteers who received the experimental vaccine are doing well. They reported only mild, temporary side effects like arm pain and fatigue, similar to routine vaccinations, according to infectious disease specialist Maheshi Ramasamy.

The vaccine uses the same proven technology as the Oxford AstraZeneca COVID-19 vaccine, which has been safely administered billions of times globally. Researchers plan to enroll 25 more participants in the UK and 50 in Ghana before moving to larger trials in Nigeria and other affected countries.

Lassa fever spreads to humans mainly through food or water contaminated by infected rats, and can also pass between people through bodily fluids. The illness starts with fever and weakness but can quickly progress to bleeding, respiratory problems and organ failure without early treatment.

In 2025 alone, Nigeria recorded 206 deaths from the disease. Many survivors face lifelong complications including hearing loss and neurological problems, making prevention critical.

For decades, vaccine development stalled because Lassa fever mainly affects low and middle income countries, offering little profit for pharmaceutical companies. The Coalition for Epidemic Preparedness Innovations stepped in to fund research after the devastating 2014-2016 Ebola outbreak exposed this gap.

Nigeria is already hosting other Lassa fever vaccine studies, including a Phase 2 trial by another developer. The country has strengthened its clinical trial infrastructure and established the Lassa Fever Coalition alongside Liberia, Sierra Leone, Guinea and Benin Republic to ensure future vaccines are accessible and affordable.

The Ripple Effect

Researchers aren't putting all their eggs in one basket. Multiple vaccine candidates are moving through development simultaneously, a lesson learned from COVID-19 when relying on single solutions slowed global response.

Community engagement teams are already working in Nigeria, Liberia and Sierra Leone to understand vaccine hesitancy and build trust before larger trials begin. This early groundwork ensures communities most affected by the disease will have a voice in how prevention tools are introduced.

The experimental vaccine aims to prevent infection, not treat those already sick, but that prevention could save hundreds of lives and spare countless families from losing loved ones to a disease that has haunted the region for generations.

After five decades of waiting, West Africa is one step closer to protection from Lassa fever.