Why is there still no licensed vaccine for Bundibugyo ebolavirus? Lessons from the 2026 outbreaks in Uganda and the Democratic Republic of Congo

Dear Editor,

The Bundibugyo ebolavirus (BDBV) outbreaks reported in Uganda and the Democratic Republic of Congo (DRC) in 2026 occurred in settings with long experience of Ebola yet again without access to a licensed, species-specific vaccine. Earlier outbreaks in Uganda and DRC have already demonstrated that BDBV can cause substantial morbidity and mortality and that delayed detection and response amplify case-fatality and health-system disruption [1]. These events revived long-standing concerns that global preparedness remains narrowly focused on Zaire ebolavirus (EBOV), leaving non-Zaire species dangerously neglected.

Over the past decade, EBOV vaccine development has progressed from early candidates to licensed products, including rVSV-ZEBOV (Ervebo) and Ad26.ZEBOV/MVA-BN-Filo, supported by intensive public–private investment during and after the 2013–2016 West Africa epidemic [2]. These vaccines have demonstrated high effectiveness in ring-vaccination strategies and durable immune responses in African healthcare workers [2]. However, their indication is essentially limited to EBOV, and they do not protect against BDBV or Sudan virus, which have repeatedly caused outbreaks in Uganda and neighbouring countries [2]. In contrast, BDBV remains without a licensed vaccine despite proof-of-concept efficacy of BDBV-specific and multivalent candidates in animals and strong immunological rationale for cross-species vaccine design [3].

The reasons for this failure are structural rather than scientific. First, limited commercial incentives discourage late-stage development and licensure for pathogens that cause sporadic outbreaks in low-income settings; even for EBOV, post-licensure access for at-risk countries has been constrained [2]. Second, BDBV outbreaks are unpredictable and relatively infrequent, complicating traditional efficacy trials within their short temporal window, as experienced for Sudan virus outbreaks and experimental countermeasures in Uganda [1]. Third, funding has prioritised EBOV-focused platforms; many advanced vaccines and immunogen-design efforts were built around EBOV glycoprotein, with BDBV incorporated late—if at all—into trivalent or “pan-ebolavirus” concepts [2]. This dependency on EBOV-centric platforms slows the tailored optimisation and regulatory path for BDBV. Finally, regulatory and logistical pathways for licensure using animal-rule evidence, established for EBOV, have not been systematically extended to non-Zaire filoviruses despite robust BDBV animal efficacy data [3].

The public health implications of entering each new BDBV outbreak without an approved vaccine are profound. Diagnostic and response delays in Uganda have been associated with higher Ebola case-fatality ratios, underscoring the life-saving impact of earlier, more decisive interventions [1]. In the absence of a licensed BDBV vaccine, containment relies on intensive case management, infection prevention and control, and ad hoc deployment of experimental products, exposing healthcare workers and already fragile health systems in Uganda and DRC to avoidable risk and repeated service disruption [1]. Preparedness investments around DRC's EBOV outbreaks have yielded durable capacities, but remain skewed toward reactive, short-term surge support rather than sustainable systems for research, licensure, and equitable access to countermeasures, including for non-Zaire filoviruses [4].

Continuing to accept a reactive model is no longer tenable. Animal and immunogen-design studies show that multivalent or immuno focused vaccines can elicit broad responses against EBOV, BDBV, and Sudan virus without compromising strain-specific immunogenicity [3]. Proof-of-concept BDBV-specific vaccines, including rVSV-based constructs and intranasal trivalent platforms, have protected non-human primates and small animals from lethal challenge, directly addressing the putative scientific “barrier” to BDBV vaccine feasibility [3]. The remaining gap is one of political will, financing, and regulatory prioritisation.

To close this critical hole in global health security, several actions are urgent. First, multivalent Ebola vaccines that include BDBV antigens and demonstrate cross-protective immunity should be fast-tracked through coordinated international funding and streamlined regulatory pathways, building on EBOV licensure experience [2]. Second, clinical research specifically on BDBV vaccine candidates must be expanded, including preparedness protocols, pre-approved trial designs, and standing platforms in high-risk African regions [1]. Third, sustainable financing mechanisms—beyond outbreak-linked emergency funds—are needed to support late-stage development, stockpiling, and equitable access for non-Zaire filoviruses [5]. Fourth, regional research collaborations in Africa, particularly between Uganda and DRC, should be strengthened to co-lead BDBV vaccine and diagnostics development, enhancing ownership and context-appropriate implementation [1]. Finally, vaccine preparedness for all human-pathogenic ebolaviruses must be fully integrated into broader epidemic-preparedness frameworks and International Health Regulations implementation, with explicit attention to vaccine equity, healthcare-worker protection, and resilient health systems [1].

In conclusion, the absence of a licensed Bundibugyo ebolavirus vaccine after repeated outbreaks is not an inevitability of virology but a consequence of policy choices. Correcting this imbalance is essential to credible epidemic preparedness, protection of African health workers and communities, and global health security.

Ethical approval

This study did not involve any human or animal subjects, and thus, did not require review by an Institutional Review Board (IRB).

Ethical approval

Not applicable.

Source of funding

The authors have not been recipients of any funding for this specific study. Not applicable.

CRediT authorship contribution statement

Aniso Mohamed Abdi: Conceptualization, Investigation, Writing – original draft, Writing – review & editing. Ahmed Mohamed Omar: Conceptualization, Methodology, Resources. Ilyas Abdullahi Khalif: Formal analysis, Investigation, Visualization. Abdirahman Mohamed Adan: Data curation, Methodology, Software. Sharmake Gaiye Bashir: Data curation, Supervision, Writing – review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.