West Nile Virus Vaccines 2023

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Last reviewed
September 1, 2023
Content Overview
West nile virus vaccine candidates are conducting clinical trials in 2023.

West Nile Virus Vaccine Candidates 2023

As of September 2023, no U.S. Food and Drug Administration (FDA)-approved West Nile virus (WNV) vaccines are available for people. However, active human clinical studies include several vaccine candidates: two live attenuated chimeric, one DNA, one recombinant subunit, and two inactivated whole-virus vaccines.

In phase 2 trials, the live attenuated recombinant yellow fever vaccine strain expressing the premembrane and envelope (prM–E) genes of WNV (ChimeriVax-WN02, Sanofi Pasteur) was found to have a good safety profile and immunogenicity even in older age groups after a single dose.

The HydroVax-001 vaccine candidate consists of a hydrogen peroxide inactivated whole virion (WNV-Kunjin strain) adjuvanted with aluminum hydroxide.

"Our experience over the past two decades has demonstrated that current prevention strategies are insufficient to reduce the ongoing WNV disease burden. WNV vaccination would be more effective in preventing WNV disease and related deaths," wrote a Perspective published by the NEJM on May 4, 2023. "Although serious adverse events were not reported in early clinical trials, potential safety concerns must be addressed in future WNV vaccine development efforts. The benefits of live vaccines, including durability of immunity and the need for only one dose, will need to be weighed against potential safety concerns."

West Nile Virus Outbreaks 2023

Since 1999, West Nile Virus (WNV) has become the leading cause of arthropod-borne viral (arboviral) disease in the United States, says the U.S. Centers for Disease Control and Prevention (CDC). As of August 29, 2023, thirty-six U.S. States have reported 455 human WNV cases and 315 Neuroinvasive Human Disease (meningitis or encephalitis) patients. The CDC updates season WNV data every week from May through December. In 2022, a total of 1,126 cases of WNV disease in people were reported, led by Arizona, Colorado, and California. In Maricopa County, (Phoneix) Arizona, 1,487 WNV cases were reported in 2021, and 68% were hospitalized. Of these, 737 (71%) were classified as neuroinvasive diseases, and 7% were related deaths. Over the last five years, Texas has had 485 WNV cases and 65 associated deaths.

In Europe, a total of five human cases of WNV infection (Greece (3), Hungary (1), and Italy (1)) have been reported from EU/EEA countries since the beginning of the 2023 transmission season and as of July 26, 2023. The Nouvelle-Aquitaine Regional Health Agency received a report on July 27, 2023, of the first autochthonous human case of West Nile virus infection in a person residing in Bordeaux, France. This is the first time WNV has been transmitted to humans other than France's Mediterranean coast, Occitanie, and Provence-Alpes-Côte d'Azur regions. 

A study published in the Journal of Experimental Medicine on June 22, 2023, found that about 35% of patients hospitalized for WNV also carried autoantibodies that neutralize type 1 interferons, the signaling proteins deployed by various cells in the fight against viruses.