Evaluation of Access to Licensed Ebola Vaccines for High-Risk Infectious Diseases

Overview

This review analyzes the current landscape of licensed Ebola virus disease (EVD) vaccines, highlighting progress in vaccine development, stockpiling, and deployment. Despite advances, challenges remain in vaccine access, stock management, and implementation strategies, which may impact outbreak control and prevention efforts.

Background

Ebola virus disease (EVD), caused primarily by the Orthoebolavirus zairense species, remains a significant public health threat due to zoonotic spillover and human-to-human transmission. EVD outbreaks have caused high mortality, with case fatality ratios averaging 67% but reducible to 25% with supportive care and vaccination. Recent outbreaks have underscored the unpredictable nature of EVD transmission, including viral persistence in survivors. In response, rapid vaccine development led to licensure of multiple vaccine regimens and establishment of global stockpiles to support outbreak response.

Data Highlights

Key Findings

• Four licensed Ebola vaccine regimens exist, with two WHO-prequalified: Ervebo (single-dose) and Zabdeno/Mvabea (two-dose).
• Ervebo underwent the fastest WHO prequalification process to date and is stockpiled globally for outbreak response.
• Ring vaccination strategies using Ervebo target direct and secondary contacts to interrupt transmission chains effectively.
• Despite stockpiling, vaccine demand has been limited due to successful outbreak containment, leading to dose repurposing or expiration.
• Recent outbreaks show a shift with nearly half originating from viral persistence rather than zoonotic spillover, emphasizing survivor follow-up and vaccination.
• Updated 2024 WHO SAGE recommendations clarify vaccine use: Ervebo for outbreak response and contacts of survivors; either vaccine regimen for preventive use in at-risk populations.

Clinical Implications

Clinicians and public health officials should prioritize vaccination of high-risk contacts and survivors with documented viral persistence using the single-dose Ervebo vaccine during outbreaks. Preventive vaccination programs using WHO-prequalified vaccines should be implemented in at-risk populations to reduce outbreak incidence. Ongoing monitoring of vaccine stockpiles and expiration is critical to ensure timely availability and avoid wastage.

Conclusion

Significant progress has been made in licensing and deploying Ebola vaccines, yet challenges in vaccine access, stockpile management, and evolving outbreak dynamics necessitate continued efforts to optimize immunization strategies. Addressing these bottlenecks is essential to sustain effective EVD outbreak control and prevention.

References

1. WHO/UNICEF/Gavi 2024 -- Ebola Virus Disease Vaccine Implementation and Stockpile Management
2. CDC 2023 -- Ebola Virus Disease Transmission and Epidemiology
3. SAGE 2024 -- Updated Recommendations on Ebola Vaccination