NIH launches trial of Lassa fever vaccine
Key takeaways:
- The candidate vaccine is based on a modified, weakened rabies virus vaccine.
- There are no approved vaccines or treatments for Lassa fever, which is caused by a virus carried by West African rodents.
The NIH announced the beginning of a phase 1 first-in-human trial of a vaccine for Lassa fever, a potentially fatal viral hemorrhagic disease for which there is no approved vaccine or treatment.
The trial, which started enrolling participants at the University of Maryland School of Medicine this month, will test Lassarab, an experimental vaccine against Lassa virus that uses an existing rabies vaccine platform.
“Effective vaccines against emerging viral pathogens for which there are no specific antiviral therapies remains the most important mechanism for the control and mitigation of the potential catastrophic effects of emerging pathogens,” Wilbur H. Chen, MD, MS, FACP, FIDSA, chief of the division of geographic medicine at University of Maryland School of Medicine and sponsor of the vaccine trial, told Healio.
Lassa fever is a rat-borne viral disease that was first identified in Nigeria in 1969 after three nurses were infected with a then unknown pathogen that caused acute hemorrhagic disease.
The infection is endemic in West Africa — including in Guinea, Liberia, Nigeria and Sierra Leone — and causes an estimated 100,000 to 300,000 cases and roughly 5,000 deaths per year, according to the CDC. There have been nine travel-related cases of Lassa fever in the United States, including one last year in Iowa.
According to the CDC, ribavirin is often used to treat Lassa fever symptoms. Among the Lassa fever vaccines in development, one started a phase 2 clinical trial last year, according to CEPI, making it the first Lassa vaccine candidate to ever reach phase 2.
The NIH-funded trial, which is led by Justin R. Ortiz, MD, MS, FACP, FCCP, professor of medicine at the University of Maryland School of Medicine, will enroll as many as 55 adults aged 18 to 50 years, who will receive two injections, 28 days apart, of one of three concentrations of the candidate vaccine.
Lassarab uses a deactivated rabies virus “that has been engineered to express the Lassa fever virus glycoprotein, which is hypothesized to be the protective moiety or antigen against which protective immune responses might protect against a Lassa fever virus infection,” Chen explained.
“It is very possible that the Lassarab vaccine candidate could be an effective vaccine for both Lassa fever and rabies,” Chen said, although he noted that its use against rabies would be to be studied separately.
“Nonetheless, I would hypothesize that Lassarab, as an inherent rabies virus-based vaccine, might prove to be interchangeable with existing rabies vaccines — a prediction that presumes that the vaccine elicits similar protective responses as monovalent rabies vaccines,” he said.
For more information:
Wilbur H. Chen, MD, MS, FACP, FIDSA, can be reached at wchen@som.umaryland.edu.
Justin R. Ortiz, MD, MS, FACP, FCCP, can be reached at jortiz@som.maryland.edu.
References:
- CDC. Lassa fever: About Lassa fever. https://www.cdc.gov/lassa-fever/about/index.html. Updated Jan. 31, 2025. Accessed March 20, 2025.
- CEPI. Lassa fever. https://cepi.net/lassa-fever. Accessed March 20, 2025.
- DMID 23-0015; Lassa Fever CVD 1000. https://www.clinicaltrials.gov/study/NCT06546709. Updated March 5, 2025. Accessed March 20, 2025.
- Lassa fever suspected in death of U.S. traveler returning from West Africa. https://www.cdc.gov/media/releases/2024/s1028-lassa-fever.html. Accessed March 21, 2025.
- NIH-sponsored trial of Lassa vaccine opens. https://www.nih.gov/news-events/news-releases/nih-sponsored-trial-lassa-vaccine-opens. Published March 17, 2025. Accessed March 20, 2025.
Perspective
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Lassa fever is a severe disease with a fatality rate as high as 70% in some countries. The clinical presentation is similar to Ebola. Lassa fever is also one of the most commonly imported hemorrhagic fevers. In October, there was a fatal case of Lassa fever in Iowa. At present, there are no approved drugs or vaccines for Lassa fever.
I commend the investigators at Thomas Jefferson University for developing this promising candidate and the NIH for launching this phase 1 trial. A Lassa fever vaccine will potentially save many lives and provide the United States with an important countermeasure when the Lassa virus next appears here. The rabies vaccine platform also offers the opportunity to develop vaccines for other viruses of public health significance.
References:
Professor, Department of Microbiology and Immunology
Tulane University School of Medicine
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