WHO emergency guidance on the use of licensed Ebola virus vaccine during Bundibugyo virus disease outbreaks, 28 May 2026

Overview

This emergency guidance document outlines the World Health Organization (WHO) position on the use of the licensed Ebola virus vaccine Ervebo® during outbreaks of Bundibugyo virus disease (BVD) caused by Bundibugyo virus (BDBV). Issued in the context of the 2026 Public Health Emergency of International Concern, the document reviews available evidence regarding potential cross-protection of Ervebo®, which is licensed for Ebola virus disease caused by Ebola virus (EBOV), against BDBV infection. WHO assessed preclinical and clinical immunological evidence, operational and ethical considerations, and implications for public confidence and outbreak response.

The review concludes that current evidence on cross-protection against BDBV is very limited and insufficient to determine or reliably estimate vaccine effectiveness. Existing studies suggest possible partial heterologous immune responses, but findings are inconsistent and based primarily on small nonhuman primate studies and laboratory immunological analyses. WHO therefore recommends that Ervebo® should not be used programmatically in response to BDBV outbreaks outside controlled research settings.

The document emphasizes that outbreak control should continue to rely on established public health measures, including surveillance, contact tracing, clinical management, infection prevention and control, and community engagement, while calling for accelerated development and evaluation of BDBV-specific and broadly protective filovirus vaccines.