The National Institutes of Health (NIH) has initiated a clinical trial to test a vaccine candidate aimed at preventing Lassa fever, a severe viral hemorrhagic disease that can be fatal and often causes permanent hearing loss in survivors. The trial, sponsored by NIH’s National Institute of Allergy and Infectious Diseases (NIAID), is currently enrolling participants at the University of Maryland School of Medicine in Baltimore.
Lassa fever is primarily transmitted to humans through contact with rodents known as multimammate rats, which are common in many West African countries. Person-to-person transmission is also possible. With no approved vaccines or specific treatments available, the disease remains a public health concern.
Vaccine Development and Trial Details
The experimental vaccine, named LASSARAB, was developed by an NIH-supported research team at Thomas Jefferson University in Philadelphia. According to NIAID Director Dr. Jeanne Marrazzo, the vaccine’s progression from laboratory research to human clinical trials marks a significant step toward preventing Lassa fever.
The Phase 1 trial will involve up to 55 healthy adults, aged 18 to 50, who will receive two doses of the vaccine candidate or a licensed rabies vaccine used as a control. The doses will be administered 28 days apart. The trial aims to evaluate the safety and immune response (immunogenicity) triggered by three different concentrations of the LASSARAB vaccine.
Promising Preclinical Research
In preclinical studies published in 2024, Matthias Schnell, Ph.D., and his team at Thomas Jefferson University tested LASSARAB on nonhuman primates. The results showed that two doses, given 28 days apart, protected the animals from lethal exposure to Lassa virus six weeks after their second inoculation.
LASSARAB is derived from a weakened rabies vaccine that has been inactivated and modified to express both rabies proteins and a Lassa virus surface protein called the glycoprotein precursor complex (GPC). If the vaccine is proven to be safe and effective in generating immune responses against both Lassa fever and rabies, it could offer dual protection after further testing and FDA approval.
Next Steps and Additional Information
The clinical trial is part of NIH’s broader efforts to develop better prevention, diagnosis, and treatment options for infectious diseases. Detailed information about the trial can be found on clinicaltrials under the identifier NCT06546709.
NIAID, which conducts and supports research across the U.S. and globally, aims to advance scientific understanding and improve public health outcomes. More resources, including news releases and fact sheets, are available on the NIAID website.
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