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Vaccine targeting mosquito-borne viruses safely prompts immune response in clinical trial
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Rosemary Pitrone
Mosquito on person's skin

The WEVEE vaccine targets three viruses that can be transmitted to humans via infected mosquitoes: eastern equine encephalitis virus (EEEV), western equine encephalitis virus (WEEV) and Venezuelan equine encephalitis virus (VEEV).

A vaccine candidate for the prevention of several mosquito-borne viruses has been found to be safe and prompt a durable immune response in adults, according to results from a Phase I clinical trial conducted at the Hope Clinic of Emory Vaccine Center.

The findings were published in The Lancet Infectious Diseases.

The trivalent vaccine, named WEVEE, was developed by scientists at the National Institute of Allergy and Infectious Diseases (NIAID) Vaccine Research Center (VRC). NIAID, which is part of the National Institutes of Health, sponsored and funded the clinical trial.

The WEVEE vaccine targets three viruses that can be transmitted to humans via infected mosquitoes: eastern equine encephalitis virus (EEEV), western equine encephalitis virus (WEEV) and Venezuelan equine encephalitis virus (VEEV).

 The viruses are usually transmitted in swampy areas and have caused recurrent, small outbreaks throughout the Americas. While rare, they can lead to flu-like symptoms and, in some cases, severe outcomes including neurological damage and death. In 2019, an outbreak of EEEV in the northeastern U.S. led to 38 confirmed cases and 15 deaths.

The findings of the Phase I clinical trial represent the first published results of a trivalent vaccine for the prevention of EEV, WEEV and VEEV in humans. 

30 participants between ages 18 to 50 years were enrolled in the trial at the Hope Clinic. Each participant received two shots of the WEVEE vaccine, administered eight weeks apart at varying dosages. Some also received an additional adjuvant to strengthen the immune responses.

Four weeks after the second dose, all vaccine regimens were found to be safe, well tolerated and induce adequate neutralizing antibody responses. The results support further development and evaluation of the WEVEE vaccine in advanced-phase clinical trials, the investigators say.

“The WEVEE vaccine is highly efficient; a single vaccine shot contains three different mosquito-borne viruses and was able to induce immunity to all three,” says principal investigator Srilatha Edupuganti, MD. “We are pleased to have taken part in this study at the Emory Hope Clinic and looking forward to further development of this vaccine. A special thanks to the study volunteers.”

The WEVEE vaccine consists of virus-like particle (VLP) technology designed by VRC researchers using proteins from the outer shells of the mosquito-borne viruses. The vaccine itself cannot cause infection because VLPs do not contain viral genetic material.

Because the viruses can be transmitted via aerosol droplets under certain laboratory conditions, EEEV, WEEV and VEEV are classified as priority pathogens posing national security and public health risks. This clinical trial represents a significant step in developing the first approved vaccine against these viruses, for which there are no treatments.

NIAID has executed a commercialization license for the advanced development of the WEVEE vaccine candidate to the life sciences company Emergent BioSolutions. Funding for manufacturing of WEVEE clinical trial material and pre-clinical studies was funded in part by an interagency agreement between NIAID and the U.S. Department of Defense Joint Program Executive Office for Chemical, Biological, Radiological and Nuclear Defense.


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