Encephalitis vaccine does well in early clinical trial; commercial development pending

Commercial development of a vaccine against three types of mosquito-borne equine encephalitis viruses — which are classified as potential biological warfare agents and can be fatal in humans — has begun following a government-led phase I clinical trial conducted with materials produced by the Frederick National Laboratory’s Vaccine Clinical Materials Program.  

No therapies or approved vaccines exist for the three viruses, the Eastern, Western, and Venezuelan equine encephalitis viruses, which can cause flu-like and more severe symptoms. Each of these viruses can cause encephalitis, but it most often occurs in people infected with Eastern equine encephalitis virus (EEEV). Thirty percent of patients with this encephalitis will die and more than 50% of survivors will have permanent neurologic damage. 

These pathogens are classified as “priority pathogens” that pose a risk to national security and public health because there is potential for transmission by the aerosol route, as has occurred accidentally in a laboratory with Venezuelan equine encephalitis virus (VEEV). Because of this, these viruses can potentially be used as agents of bioterrorism that are delivered via the aerosol route. A vaccine would therefore be of immediate value to soldiers and to scientists whose research on countermeasures involves potential contact with the viruses. 

To address these concerns, a team of scientists at the National Institute of Allergy and Infectious Disesases (NIAID) Vaccine Research Center (VRC), which is a part of the National Institutes of Health (NIH), created a vaccine, which is called a “trivalent” vaccine, that consists of virus-like particles and induces an immune response to all three viruses. The vaccine showed promising results in a NIAID-led phase I clinical trial, as reported in The Lancet Infectious Diseases.  

NIAID subsequently licensed the technology to Emergent BioSolutions in Gaithersburg, Md. for further development as a candidate vaccine for potential regulatory approval. 

The virus-like particle vaccine contains harmless proteins from the exterior of the three viruses but none of the viral genetic material that causes infection. In the clinical trial, which was sponsored and funded by NIAID and conducted at the Emory Vaccine Center’s Hope Clinic, part of Emory University in Atlanta, the trivalent vaccine was injected into 30 healthy adult volunteers aged 18-50 at various doses and then boosted after eight weeks with similar doses of the vaccine. The vaccine was found to be safe, well-tolerated, and produced a durable immune response against all three viruses. 

“Evaluation in advanced-phase clinical trials should be done to establish optimal dosing and vaccine-administration schedule,” the scientists noted in the publication in The Lancet Infectious Diseases. 

The team that conducted the clinical trial was led by researchers at the NIAID VRC in collaboration with researchers at the study site, The Hope Clinic of the Emory Vaccine Center at Emory University in Atlanta. The study team additionally included  individuals from the Frederick National Laboratory  and the Emmes Company of Rockville, Md. 

The United States sees an average of 11 human cases of Eastern equine encephalitis per year, but saw a spike in 2019 of 38 cases with a 50 percent mortality rate, according to the U.S. Centers for Disease Control and Prevention. It is most common in certain swampy areas of the Atlantic and Gulf Coast states and around the Great Lakes.