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

The H5N1 strain of avian influenza remains an ever-present threat due to its persistent circulation among avian populations and sporadic spillover events into humans, manifesting a pandemic risk that demands urgently scalable and efficacious vaccines. Traditional influenza vaccines, typically administered via intramuscular injections, have demonstrated efficacy primarily by stimulating systemic immune responses. While protective against symptomatic disease when vaccine strains are well-matched to circulating viruses, these vaccines do not robustly induce mucosal immunity—the frontline defense at the respiratory tract, through which influenza viruses initiate infection and transmission.

Recognizing these limitations, the University of Maryland research team tested an intranasal vaccine formulation incorporating BlueWillow’s proprietary NanoVax® W_805EC adjuvant. This adjuvant is designed to enhance antigen presentation and potentiate both mucosal and systemic immune responses. The trial enrolled 40 healthy adult participants who were randomized to receive varying doses of this recombinant H5 vaccine, with control groups receiving either placebo or high-dose vaccine without the adjuvant. Six months post-administration, all participants received an intramuscular H5 booster dose, allowing researchers to evaluate priming effects conferred by the nasal vaccine.

Safety data from the trial were very encouraging: the intranasal NanoVax H5 vaccine was well tolerated with no serious adverse events reported. Critically, only subjects receiving the adjuvanted nasal vaccine demonstrated pronounced immune priming, evident as a robust immunological response to the subsequent injected booster. This priming effect was characterized by elevated titers of mucosal IgA and systemic IgG antibodies, increased frequencies of memory B and T cells, and augmented antibody-dependent cellular cytotoxicity (ADCC)—all of which are pivotal for comprehensive antiviral defense.

Importantly, this intranasal approach succeeded in eliciting cross-protective immunity against diverse clades of H5N1 viruses. This breadth of protection is significant, given the antigenic drift and evolution common to influenza viruses that often undermine vaccine efficacy. The NanoVax-adjuvanted vaccine’s ability to prime the immune system to recognize variant strains suggests a promising strategy to outpace viral mutation and provide durable pandemic preparedness.

The underlying immunological mechanisms seem to hinge on the capacity of mucosal immunization to activate specialized immune cells residing in the respiratory tract, which systemic injections alone fail to engage effectively. Mucosal IgA antibodies can neutralize pathogens at the portal of entry, while cellular immune responses facilitate rapid clearance of infected cells. The adjuvant’s role in amplifying these responses likely involves stimulation of innate immune pathways that enhance antigen uptake and presentation, thereby fostering the development of adaptive immunity.

Co-lead authors Meagan E. Deming, MD, PhD, and Franklin R. Toapanta, MD, PhD, emphasize the transformative potential of this vaccine platform—not only does it offer a needle-free, user-friendly method of administration increasing vaccine acceptance, but it also promises to stretch vaccine supplies by enabling dose sparing, an advantage during outbreak scenarios when rapid mass vaccination is essential.

The research also highlights that intranasal vaccines could significantly reduce viral transmission by establishing immunity where infection and viral shedding predominantly occur. In contrast to conventional intramuscular vaccines primarily effective at reducing severe disease, mucosal vaccination could curtail community spread by rapidly neutralizing the virus in the upper respiratory tract.

This trial’s success marks a significant milestone in influenza vaccine development by revealing tangible clinical proof of concept for mucosal vaccines against H5N1 influenza—an achievement long pursued but rarely attained in prior studies. The findings advocate for expanded clinical trials to optimize vaccine dosing, extend immunogenicity duration, and explore protection efficacy in diverse populations, including those with heightened vulnerability.

Funded by the National Institute of Allergy and Infectious Diseases, this research aligns strategically with global public health goals to curb influenza pandemics. As Mark T. Gladwin, MD, Dean of the University of Maryland School of Medicine, notes, the study accentuates the necessity of probing mucosal immune biomarkers and novel correlates of protection, both critical for accelerating the regulatory approval and deployment of next-generation intranasal vaccines.

The University of Maryland School of Medicine reinforces its reputation at the forefront of biomedical innovation, leveraging interdisciplinary expertise and cutting-edge biotechnologies to address urgent infectious disease challenges. Their Center for Vaccine Development and Global Health continues a storied legacy, having contributed significantly to vaccine advances against cholera, typhoid, malaria, and recently COVID-19, now breaking new ground in respiratory pathogen prevention.

As influenza viruses relentlessly evolve, capable of triggering potential pandemics, this novel intranasal adjuvanted H5N1 vaccine exemplifies a promising advancement. It integrates immunological insight with innovative delivery to yield a scalable, practical solution that could revolutionize influenza prevention globally — offering a beacon of hope against the relentless threat of avian influenza and enhancing pandemic preparedness.

Subject of Research: People
Article Title: An Intranasal Adjuvanted, Recombinant Influenza A/H5 Vaccine Primes Against Diverse H5N1 Clades: A Phase I Trial
News Publication Date: 6-Nov-2025
Web References: https://www.medschool.umaryland.edu/
References: DOI: 10.1038/s41467-025-64686-3
Keywords: Avian influenza, Vaccine development, Epidemics