The World Health Organization (WHO) has identified Lassa fever as a priority pathogen in urgent need of research and development due to its epidemic potential.
In a statement on Thursday, WHO announced that the Oxford Vaccine Group has vaccinated the first volunteer in a first-in-human trial of a Lassa fever vaccine.
“The first volunteer has received a dose in a first-in-human trial of a Lassa vaccine, marking a major milestone in the fight against this deadly virus,” the organization said.
The trial, conducted by the Oxford Vaccine Group and funded by the Coalition for Epidemic Preparedness Innovations (CEPI), will assess the safety and immune response of the ChAdOx1 Lassa vaccine. A total of 31 participants aged 18–55 will take part in the trial.
According to WHO, Lassa fever is caused by the Lassa virus, which is primarily spread by rodents and can lead to severe illness, including deafness, bleeding, and death.
The CEPI-funded trial is being conducted in Oxford, with a second phase 1 trial expected to begin in Ghana in early 2026.
WHO noted that Lassa fever, first discovered in Nigeria in the late 1960s, is endemic in West Africa. The organization has designated Lassa fever and related viruses as priority pathogens because of their potential to cause large outbreaks and the absence of licensed vaccines or treatments. Experts estimate that up to 700 million people could be living in regions at risk of Lassa fever by 2070.
The vaccine, developed by researchers at the Pandemic Sciences Institute, University of Oxford, uses the same viral vector platform as the Oxford/AstraZeneca COVID-19 vaccine, which is estimated to have saved six million lives in its first year.
Prof. Maheshi Ramasamy, Chief Investigator of the trial at the Oxford Vaccine Group, described vaccines as one of the most powerful tools in global health.
“They save lives, stop outbreaks, and strengthen health systems. We’re delighted to start the VITAL01 Lassa fever vaccine study here in Oxford. Building on Oxford’s world-leading experience in developing vaccines for emerging infections and pandemics, this study is a crucial step toward protecting vulnerable communities from the devastating impact of Lassa fever. CEPI also supported early preclinical development of the vaccine,” she said.
Dr. Katrin Ramsauer, Lassa Disease Programme Lead at CEPI, said the launch marked a transformative milestone in the fight against Lassa fever.
“This clinical study is the result of years of rigorous and innovative science, strong collaboration, and a deep commitment to global health. While important work lies ahead, this moment brings us closer to a future where communities no longer live in fear of this devastating disease.
“In addition to new clinical trials, plans to advance a Lassa vaccine toward licensure are progressing under the regional leadership of the Lassa Fever Coalition, led by the West African Health Organization (WAHO) with CEPI and partners. The consortium brings together West African leaders, public health experts, and vaccine developers to accelerate the equitable introduction of Lassa fever vaccines across affected regions,” she said.
Dr. Virgil Lokossou, Director of Healthcare Services at WAHO, said Lassa fever has affected lives in West Africa for more than half a century.
“Now, our region is taking bold steps to change that story. Through collaborative efforts with partners like the University of Oxford under the Lassa Fever Coalition, we are leading the way in confronting this epidemic threat so it no longer undermines our health and societies. Oxford’s vaccine candidate brings real promise, and this clinical trial comes at a time when regional efforts to defeat Lassa fever are stronger than ever,” Lokossou said.
