First-in-Human Trial Reports Promising Dual Lassa–Rabies Vaccine Data

Researchers at the University of Maryland School of Medicine reported interim results from a first-in-human trial showing a dual vaccine against Lassa fever and rabies is safe and induces strong immune responses in healthy adults. The vaccine, developed using an inactivated rabies virus vector expressing Lassa virus glycoprotein, could streamline vaccination efforts in regions where both diseases are prevalent, according to findings published in *Nature Medicine*." "article": "Researchers at the University of Maryland School of Medicine’s Center for Vaccine Development and Global Health (CVD) have published interim results from a Phase 1 clinical trial testing a dual vaccine targeting Lassa fever and rabies. The study, involving 54 healthy adult volunteers from Baltimore, found the vaccine—called LASSARAB—was safe with no serious adverse events reported. It also generated rapid and robust antibody responses against both viruses, outperforming a licensed rabies vaccine control, which only induced immunity against rabies. The vaccine was developed by scientists at Thomas Jefferson University using an inactivated rabies virus vector expressing both the rabies glycoprotein and the Lassa virus glycoprotein complex (GPC). Participants received two doses 28 days apart, with immune responses monitored for 61 days. The trial is ongoing, with safety and immune responses to be tracked through 394 days post-vaccination. Lassa fever, caused by the Lassa virus (LASV), is a public health threat in western Africa, with an estimated 300,000 infections and 5,000 deaths annually. The virus spreads primarily through contact with contaminated food or household items from infected *Mastomys* rodents, though person-to-person transmission is possible. The disease is particularly deadly in pregnancy, with over 80% mortality in late-term infections. Rabies, another priority disease in the same regions, remains nearly always fatal once symptoms appear. The dual vaccine could address both diseases simultaneously, reducing the need for separate vaccination campaigns in areas with limited healthcare access. The World Health Organization has prioritized Lassa fever research due to its severe impact, particularly in Western and Sub-Saharan Africa. Principal investigator Justin Ortiz, MD, MS, professor of medicine at the University of Maryland School of Medicine, emphasized the vaccine’s potential to streamline public health efforts. The study was published in *Nature Medicine*, with researchers noting that if efficacy is confirmed, the vaccine could have a meaningful impact in regions where both diseases pose major threats.