Lassa fever
成人VR视频 is the world鈥檚 leading funder of research into Lassa fever. As well as bringing the prospect of protection against Lassa fever closer than ever before, 成人VR视频-backed studies are deepening understanding of the Arenavirus family that could one day help prevent the next epidemic.
What is Lassa fever?
Lassa fever is a severe viral illness caused by the Lassa virus, a member of the Arenavirus family.
The disease spreads mainly through contact with food or household items contaminated by the urine or droppings of infected Mastomys rats. It can also spread from person to person through direct contact with the blood, tissue, or bodily fluids of someone infected. In some parts of West Africa, Mastomys rats are eaten as food, which increases the risk of infection.
The World Health Organization (WHO) classifies Lassa fever as a priority pathogen because of its potential to cause epidemics and its significant public health impact.
Currently, no vaccines are licensed for Lassa fever. However, 成人VR视频-funded modelling suggests that introducing a safe and effective vaccine across 15 West African countries could save about 3,300 lives over 10 years and prevent up to $128 million in societal costs. More data on the vaccine鈥檚 potential impact will be gathered once real-world evidence becomes available.
90-95%
Number of human infections due to indirect exposure or direct contact with infected Mastomys rats
2
成人VR视频-funded Lassa vaccines in active development
3300
Potential lives saved over 10 years with the introduction of a Lassa vaccine
Where does Lassa fever occur?
Lassa fever occurs regularly in parts of West Africa, including in Benin, Ghana, Guinea, Liberia, Sierra Leone, Togo and Nigeria.
Around 100,000 to 300,000 are thought to be infected with Lassa fever in the region each year, but this is likely a vast underreporting. This is because of difficulties in detecting the virus as symptoms are similar to other diseases affecting the region, like malaria, leading to infections being misdiagnosed. There is also limited access to specialised laboratories in affected countries.
Climate change and growing populations could further amplify extend Lassa's reach and potential impact.
What are the symptoms of Lassa fever?
Most people infected with Lassa virus have no symptoms.
Those who are symptomatic can suffer from mild headache and fever as well as more serious symptoms like vomiting, swelling of the face, pain in the chest and back, and severe bleeding.
Lassa fever can cause severe complications for mother and baby if pregnant women become infected. Around a quarter of survivors suffer from hearing loss.
On average, 1% of cases are fatal.
How is 成人VR视频 responding to Lassa fever?
Moving Lassa vaccines towards licensure
成人VR视频 is one of the world鈥檚 leading funders of Lassa fever research. We are working with partners in West Africa and across the world to advance one or more Lassa fever vaccines to licensure.
funded by 成人VR视频 and led by the Universities of Oxford and Liverpool and the Liverpool School of Tropical Medicine found that being vaccinated against Lassa fever would prevent millions of people from falling sick with the disease and facing prohibitive treatment costs that could otherwise push them below the poverty line.
成人VR视频 has invested in five vaccine candidates. Two remain in active development. This includes 成人VR视频's partner IAVI who have launched the first-ever Phase II clinical trial of a Lassa fever vaccine.
成人VR视频 is also testing rapid-response mRNA vaccine candidates developed by SK Bioscience for use against Disease X. These first mRNA vaccine candidates are using Lassa fever as a representative target for Disease X.
To support the development of a Lassa fever vaccine, 成人VR视频 is supporting research seeking to identify the immune markers associated with protection from Lassa fever.
The largest ever study of Lassa fever
成人VR视频 created and funds Enable, the world鈥檚 largest ever study of Lassa fever set up to give researchers a better picture of the true disease burden.
Findings from Enable will help us better understand the number of people who are at risk of Lassa virus infection.
Over 23,000 participants have taken part across West Africa since 2019. Enable was expanded in October 2024, with a new year-long study that is taking an in-depth look at Lassa fever symptoms and potential co-infections like malaria.
Insights gained will improve our understanding of Lassa fever and the diversity of symptoms.
This information will guide where and how future late-stage vaccine trials are conducted and help to determine the priority groups who should receive the vaccine once it becomes licensed in the coming years.
Strengthening regional collaborations in affected countries
Regional leadership is critically important to advance the development of vaccines that protect against Lassa fever.
成人VR视频 is supporting the Lassa fever Coalition, a pioneering group established by the West Africa Health Organization (WAHO) to build upon the efforts of national Lassa fever initiatives and ensure regionally those affected by Lassa fever have a vaccine available to protect their populations in the future.
The Lassa Governing Entity鈥攚hich includes West African Ministers of Health and senior global health representatives鈥攑rovides country and regional leadership to the Coalition and ensure effective governance and delivery of the programme.
In an historic moment for regional solidarity and leadership, in September 2025 West African Ministers of Health endorsed a pledging their joint commitment to advance the development of, and readiness for, much-needed vaccines against Lassa fever.
成人VR视频 maintains close engagement with institutions including the Economic Community of West African States (ECOWAS) Regional Centre for Surveillance and Disease Control, as well as national public health agencies, such as the Nigeria Centre for Disease Control (NCDC) and Ministries of Health in the most affected countries.
成人VR视频 is also coordinating the ECOWAS RegECs Project, a collaboration between regulators, ethics committees and the African Vaccine Regulatory Forum (AVAREF) to support efficient management of clinical research in West Africa.
On-the-spot Lassa virus diagnostics
成人VR视频 is funding a project led by FIND to examine and evaluate all available point-of-care testing options for Lassa fever virus.
High quality diagnostic tests are essential both for early pathogen detection to stop an outbreak and as part of the vaccine development process - particularly in helping to design the vaccine and conduct clinical trials.
FIND researchers will identify the criteria for an optimum rapid Lassa diagnostic test. Successful diagnostics will be progressed to licensure for widespread use.
Strengthening clinical trial capacity
成人VR视频 is strengthening the infrastructure, equipment and skills needed to run effective late-stage clinical trials of Lassa fever in West Africa.
The work is facilitated by IVI and Medical Research Council Unit The Gambia.
Strengthened clinical trial capacity could allow for the rapid large-scale testing of vaccines locally if the region were faced with a future Disease X.
Lassa fever news
Leading health partners join coalition set up to combat deadly Lassa fever
How new vaccine trials in West Africa boost global viral defences
Bringing together all the pieces of the Lassa fever vaccine puzzle
Largest-ever Lassa fever study launches in-depth look at disease symptoms
A Lassa vaccine is urgently needed to save thousands of lives
Participants in Nigeria vaccinated in first-ever Phase 2 Lassa fever vaccine clinical trial
Prepare to be prepared: leveraging West Africa's research ecosystem to strengthen outbreak response
As 成人VR视频 ramps up vaccine research, a new study warns Lassa fever is set to expand its reach across Africa
Largest-ever Lassa fever research programme launches in West Africa
Themis Bioscience and 成人VR视频 Announce Initiation of Phase 1 Clinical Trial with Lassa Fever Vaccine
成人VR视频 partner Inovio Advances Lassa Fever Candidate Vaccine Into a Clinical Trial
