A new vaccine for Lassa fever shows promise in preventing serious illness and fatalities in animals.
Researchers from Thomas Jefferson University and the University of Maryland Baltimore, in conjunction with the United States Army Medical Research Institute of Infectious Diseases (USAMRIID) and the Geneva Foundation, have created a new vaccine candidate that could protect against Lassa fever. The findings, published in npj Vaccines on August 9, 2024, reveal that this vaccine effectively prevents severe manifestations of the disease as well as death in animal models, setting the stage for human trials.
Currently, several candidate vaccines for Lassa fever are in the works. However, Dr. Matthias Schnell, who directed the Jefferson Center for Vaccines and Pandemic Preparedness at Thomas Jefferson University and co-led the study, highlighted that their LASSARAB vaccine has a competitive edge. He explained that the other two vaccines in development utilize live viral vectors, which pose potential safety concerns. “In contrast, our vaccine is a deactivated or killed formulation, which is generally regarded as safer,” he stated.
The LASSARAB vaccine employs a deactivated rabies virus to deliver antigens that protect against the Lassa fever virus. Lassa fever, a severe hemorrhagic illness endemic in parts of West Africa, results in an estimated 300,000 to 500,000 infections and over 5,000 deaths annually. It can lead to serious complications, including organ failure, hearing loss, and lasting neurological problems. Presently, there are no licensed vaccines available to prevent Lassa fever.
“The impact on patients is devastating,” said Dr. Kathleen Cashman, a virologist and principal investigator at The Geneva Foundation, which supports USAMRIID. “The virus infects and damages cells, leading to multiple organ failures, which can be lethal. It is a highly severe disease and challenging to protect against. Finding a way to prevent mortality is remarkable.”
The research involved testing the vaccine on 12 young non-human primates, with half receiving two doses of the LASSARAB vaccine, while the other half were given CORAVAX, a COVID-19 vaccine, as a control group. Though both vaccines used rabies as a vector, the antigens to trigger an immune response differed. Over a span of 28 days, the control group showed more severe symptoms, significant organ damage, and did not survive, while the group vaccinated with LASSARAB experienced less damage and survived until the study’s conclusion. The researchers noted the necessity of further studies to understand the persistence of the disease in young animals better.
While the vaccine was effective in preventing severe illness and fever, it did not stop infection. The team believes that the 28-day study might have been insufficient to evaluate the vaccine’s ability to confer long-lasting immunity. They are hopeful that longer studies involving older animals will yield more insights into the potential long-term effects of the vaccine.
The rabies virus platform utilized in the LASSARAB vaccine was developed in Dr. Schnell’s lab and presents several significant benefits. Besides providing protection against Lassa fever, the vaccine also offers defense against rabies, which is essential in many areas where Lassa is common. Previous research has indicated that a similar rabies-based vaccine for the Ebola virus remains stable under various temperatures, even at 50 degrees Celsius for up to two weeks. Dr. Schnell, who also chairs the Department of Microbiology and Immunology at Sidney Kimmel Medical College, emphasized that rabies vaccines are well-regarded for their safety, making them suitable for children and immunocompromised individuals. This dual protection is especially advantageous in regions where both diseases are widespread.
“For those who are vaccinated and boosted against rabies, most individuals enjoy lifelong immunity,” Dr. Schnell explained. “We hope that the protection against Lassa fever will also be durable, which is crucial.”
The study received a $30 million grant from the National Institute of Allergy and Infectious Diseases (NIAID), which has been instrumental in moving the vaccine candidate to this pivotal stage. “Such initiatives require government and nonprofit backing,” Dr. Schnell noted, adding that the team is thankful for this support, given the limited commercial interest from pharmaceutical companies for such vaccines. “This isn’t a SARS-CoV-2 vaccine. Our focus is on neglected infectious diseases affecting economically disadvantaged regions—people who urgently need assistance.”
Looking ahead, Dr. Schnell’s vaccine for Lassa fever is set to enter phase 1 clinical trials in November after successfully completing the Investigational New Drug (IND) application process with the Food and Drug Administration.
