WHO restricts Ervebo use in Bundibugyo outbreak

The World Health Organization (WHO) has declined to widely distribute the Ervebo Ebola vaccine in response to the deadliest Ebola outbreak currently raging in the Democratic Republic of Congo (DRC). The organization's decision stems from the insufficient available evidence confirming whether the vaccine offers meaningful protection against the Bundibugyo strain responsible for the high mortality rates in the outbreak.

The updated emergency guidance, published on WHO's official website, follows a review of additional scientific evidence by WHO's Strategic Advisory Group of Experts on Immunization (SAGE), which concluded on August 19. The Bundibugyo strain, which has now claimed 2,911 lives and affected over 6,000 individuals, has no approved vaccine.

WHO's decision was based on limited and inconclusive evidence, with animal studies suggesting some potential protective effects, but human studies showing weaker immune responses compared to the Zaire Ebola virus, for which the Ervebo vaccine was developed. Anecdotal reports involving vaccinated health workers were deemed too limited and unreliable to establish Ervebo's protective effects against Bundibugyo infection, severe illness, or death.

WHO recommends a well-designed, randomized controlled trial to determine the vaccine's effectiveness against the Bundibugyo strain, emphasizing the need for rapid implementation and scientific integrity. This decision marks a significant shift in the global response to the Bundibugyo outbreak, following intensified efforts to identify vaccines and treatments for the strain.

Ervebo is currently the only licensed Ebola vaccine available, approved to protect against the Zaire Ebola virus. Earlier this year, the advisory group recommended prioritizing Ervebo for inclusion in a Phase 3 trial during the ongoing Bundibugyo outbreak. The DRC outbreak is already the deadliest in the country's history, and containing it remains challenging due to factors such as insecurity, population displacement, and limited access to some communities, complicating contact tracing and other public health interventions.

Beyond the immediate health crisis, a wider spread of the outbreak could have severe economic consequences for Africa, with the United Nations Development Programme estimating that an Ebola outbreak could cost the continent up to $3.6 billion in economic output and lead to over 328,000 job losses.