Equine encephalitis


  • MVA-BN® WEV has completed Phase 1 clinical development demonstrating potential for broad, and long-term protection
  • Development funded by the U.S. Department of Defense
  • Phase 2 planned for 2024

MVA-BN WEV is a multi-valent vaccine candidate developed under contracts with the US government to address the unmet medical need for a vaccine against western, eastern and Venezuelan equine encephalitis viruses, which are rare, but potentially deadly viruses transmitted to humans by mosquitos.

The first contract valued up to USD 36 million was awarded by the U.S. Department of Defense (DoD) in 2018 and included the demonstration of protective efficacy in animals and a Phase 1 first-in-human trial of MVA-BN WEV. Results from this trial were reported in 2020, showing that the vaccine was well tolerated and immunogenic across all dose groups. Neutralizing antibody responses were observed against Venezuelan equine encephalitis virus in all dose groups, with peak levels reached after the second vaccination. Recent data has confirmed neutralizing antibody responses also against western and eastern equine encephalitis viruses that were durable throughout the six-months follow up period.

In December 2022, we entered a new agreement valued up to USD 83 million with DoD for the advanced development of MVA-BN WEV. The base agreement of USD 55 million has been secured for the period 2023-2026 and covers the costs for a clinical Phase 2 dose finding study of MVA-BN WEV, further non-clinical studies, process development and manufacturing of clinical trial material. Furthermore, the agreement includes options valued at USD 28 million to support Phase 3 preparations.

Western, Eastern and Venezuelan equine encephalitis viruses belong to the family alphavirus, and are transmitted through mosquitos, as well as birds and some mammals. While the viruses vary in infection rates and severity of disease, all three pathogens are associated with risks of flu-like symptoms, potential central nervous disorders, and death. All three viruses are considered as potential biological threats, having been investigated as potential biological weapons at various times in the past century. The viruses belong to the U.S. list of prioritized pathogens amongst other agents, like smallpox, anthrax and other lethal diseases, which are covered by the current vaccination policy for U.S. military personnel being deployed around the globe. However, there are currently no approved vaccines for human use against any of the equine encephalitis viruses.

In recent years, the U.S. has seen a rise in human cases of eastern equine encephalitis, particularly in the southern and northeastern parts of the country, correlating with increased observations of mosquitos carrying the virus in these regions. According to the U.S Centers for Disease Control and Prevention (CDC), 38 cases were reported in 2019, compared to an annual average of 7 cases over the past decade. On average, more than 4 of 10 infected individuals die after contracting the virus.