Early positive results for mosquito-borne virus vaccine  

A vaccine for a range of mosquito-borne viruses has received positive results from a Phase I clinical trial. 

Scientists at the National Institute of Allergy and Infectious Diseases (NIAID) Vaccine Research Center (VRC) have developed a vaccine for eastern equine encephalitis virus (EEEV), western equine encephalitis virus (WEEV), and Venezuelan equine encephalitis virus (VEEV). 

EEV, WEEV and VEEV are spread to humans through the bites of infected mosquitoes. Whilst infections are rare in humans, the viruses can cause flu-like symptoms and, in some cases, severe neurological damage or death. 

Under certain laboratory conditions, the viruses can transmit through the air by aerosol droplets and cause infection in humans and are therefore classified as priority pathogens, by the NIAID, potential biological agents that pose a risk to national security and public health. NIAID has highlighted a possible use of a EEEV vaccine for those working in high-risk areas of the disease, such as members of the military and laboratory workers.  

Scientists at the VRC have developed a designed a virus-like particle (VLP) vaccine candidate (abbreviated WEVEE) that uses proteins from the outer shells of the EEE, WEE and VEE viruses to prompt an immune response. VLPs do not contain the genetic material that the viruses need to replicate inside cells, so VLPs cannot cause infection.  

Results from a Phase I clinical trial 1 of 30 volunteers showed the vaccine to be safe, well-tolerated and that induced durable immune responses against all three viruses. Participants first received varying doses of the WEVEE vaccine (6, 30 or 60 micrograms) by intramuscular injection and then received a booster dose eight weeks later.  

Some participants also received a formulation of the experimental vaccine that contained an alum adjuvant added to increase immune responses. The highest neutralising antibody response was observed in participants who received the 30-microgram dose with adjuvant. 

NIAID has now executed a commercialisation license for the advanced development of the WEVEE vaccine candidate to the life sciences company Emergent BioSolutions in Gaithersburg, Maryland. 


1: E Coates et al. Safety and immunogenicity of a trivalent virus-like particle vaccine against western, eastern, and Venezuelan equine encephalitis viruses: a phase 1, open-label, dose-escalation, randomised clinical trial. The Lancet Infectious Diseases DOI: 10.1016/S1473-3099(22)00052-4 (2022). 

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