West Nile Virus Vaccines

West Nile Virus Vaccine Candidates 2025

The US Food and Drug Administration (FDA) has not approved West Nile virus (WNV) vaccines for use in humans as of December 2025. However, active human clinical studies include vaccine candidates: two live attenuated chimeric vaccines, one DNA vaccine, one recombinant subunit vaccine, and two inactivated whole-virus vaccines. A Research Article published in October 2025 stated that live-attenuated vaccines, including flavivirus YFV 17D and JEV SA14-14-2 vaccines, offer the advantages of robust immune responses and long-lasting protection.

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) demonstrated a favorable safety profile and immunogenicity, even in older age groups, following 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. "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."