In a groundbreaking development poised to transform infectious disease prevention, researchers at the University of Maryland School of Medicine’s Center for Vaccine Development and Global Health (CVD) have reported promising results from a phase 1 clinical trial of a novel dual vaccine targeting both Lassa fever and rabies. Published recently in the prestigious journal Nature Medicine, the study demonstrates that this innovative vaccine candidate is not only safe but also capable of eliciting strong immune responses against two of the most deadly viral threats endemic to regions of Africa. This milestone represents a crucial step forward, especially considering that no licensed vaccines currently exist for Lassa fever, a neglected tropical disease with devastating consequences.
Lassa fever, caused by the Lassa virus, is an acute viral hemorrhagic illness primarily transmitted to humans via contact with multimammate rats, prevalent in West Africa. The World Health Organization classifies Lassa fever as a priority pathogen due to its capacity to cause severe outbreaks with high mortality rates and its potential to expand geographically, a trend exacerbated by ongoing climate change. It is estimated that approximately 300,000 infections and 5,000 deaths occur each year in western Africa, though these figures likely underestimate the true burden owing to limited disease surveillance infrastructures. Crucially, Lassa fever poses an alarming risk during pregnancy—especially in the late stages—where mortality rates for expectant mothers and fetuses soar to above 80%, highlighting the urgent need for effective preventive strategies.
Regions plagued by Lassa fever frequently contend with another equally devastating viral disease: rabies. Rabies, caused by the rabies virus, results in tens of thousands of human fatalities annually across much of sub-Saharan Africa. Once the clinical symptoms of rabies emerge—typically encephalitis and paralysis—the disease is almost invariably fatal, underscoring the necessity for preventive vaccination. The presence of overlapping geographies afflicted by both Lassa fever and rabies complicates public health responses and amplifies the burden on healthcare delivery systems.
“The development of a combined vaccine targeting these two viruses is a strategic breakthrough,” stated Dr. Justin Ortiz, a Professor of Medicine at UMSOM and principal investigator of the study. “By integrating immunogenic components against both pathogens into a single vaccine platform, we hope to simplify vaccination logistics and expand coverage, particularly in resource-limited settings where these diseases impose the greatest toll.”
The clinical trial enrolled 54 healthy adult volunteers from the Baltimore area who were randomized to receive varying doses of the experimental vaccine, named LASSARAB, formulated with an adjuvant, or a licensed rabies vaccine as control. Participants received two immunizations spaced 28 days apart. Immune responses were monitored through 61 days post-vaccination for an interim safety and immunogenicity analysis. Remarkably, LASSARAB demonstrated a highly favorable safety profile without any serious adverse events, while eliciting robust and rapid antibody titers effective against both Lassa virus glycoproteins and rabies virus antigens. In contrast, the control vaccine only stimulated immunity against rabies virus, underscoring the dual-target specificity of LASSARAB.
This candidate vaccine utilizes an inactivated rabies virus vector engineered to express the glycoprotein complex of Lassa virus on its surface. This approach exploits the well-characterized immunogenic properties of the rabies virus platform to safely present Lassa virus antigens to the host immune system, thereby inducing protective responses against both pathogens simultaneously. Beyond immunogenicity, LASSARAB’s formulation can be lyophilized—freeze-dried—to facilitate storage and distribution without reliance on cold chain logistics, a critical advantage for deployment in remote regions lacking robust refrigeration infrastructure.
The LASSARAB vaccine was developed by a multidisciplinary research team led by Professor Matthias Schnell at Thomas Jefferson University’s Jefferson Center for Vaccines and Pandemic Preparedness. This cross-institutional collaboration highlights the vital role of bringing together expertise in virology, immunology, and vaccine technology to address emerging global health threats. With climate change driving shifts in the ecological niches suitable for Lassa virus transmission, expanding at-risk populations could reach an estimated 700 million globally by 2070, raising the stakes for proactive vaccine development.
Dean Mark T. Gladwin of the University of Maryland School of Medicine emphasized the gravity of the challenge: “The extension of Lassa fever beyond its traditional West African confines, fueled by environmental changes, makes the timely development of a safe and effective vaccine not only a regional imperative but a global health priority.” The clinical trial’s early attention from Nature Medicine in its 2025 feature naming it among the eleven most influential clinical trials to watch in 2026, further underscores the scientific and public health community’s high expectations for this innovative vaccine.
With ongoing study until nearly 400 days post-vaccination, investigators will continue to evaluate the durability of immune responses and long-term safety in trial participants. If sustained protective immunity is confirmed, LASSARAB will proceed to more advanced clinical testing phases, including larger population cohorts in endemic regions, moving closer to addressing a critical unmet need in global infectious disease control.
This first-in-human trial represents a remarkable advance born from decades of research in vaccine development and infectious disease epidemiology. The University of Maryland’s CVD, founded in 1974, has cultivated a storied legacy of pioneering vaccine-related breakthroughs, translating scientific discovery into lifesaving health interventions globally. Their mission to combat the world’s deadliest diseases through research innovation and public health implementation embodies the spirit of translational medicine that this dual vaccine exemplifies.
Ultimately, LASSARAB exemplifies the next wave of precision vaccine design—leveraging viral vectors to target complex pathogens endemic to vulnerable populations while addressing logistical challenges posed by resource constraints. The promise held by this vaccine candidate is flexible, scalable, and timely, with the potential to significantly curb mortality and morbidity from two of Africa’s deadliest diseases. As the global scientific community watches closely, the impact of this innovation could reverberate far beyond its initial trial, heralding new paradigms for combating emerging viral threats worldwide.
Subject of Research: People
Article Title: Adjuvanted inactivated rabies virus-vectored Lassa virus vaccine in healthy adults: a phase 1 trial
News Publication Date: 9-Jun-2026
Web References:
- Center for Vaccine Development and Global Health (CVD)
- Africa Centers for Disease Control and Prevention – Lassa Fever
- Jefferson Center for Vaccines and Pandemic Preparedness
- University of Maryland School of Medicine
- Nature Medicine Article DOI: 10.1038/s41591-026-04429-z
References:
Journal: Nature Medicine
DOI: 10.1038/s41591-026-04429-z
Keywords: Vaccine development, Clinical trials, Infectious diseases, Lassa fever, Rabies, Viral vector vaccine, Dual vaccine, Immunogenicity, Global health, Emerging infectious diseases, Vaccine safety, Public health
