The Democratic Republic of Congo (DRC) is confronting a burgeoning Ebola epidemic caused by the Bundibugyo virus, prompting a significant strategic pivot in its public health response. Health authorities, in collaboration with partners like Africa CDC and the World Health Organization (WHO), are moving to expand the use of the Ervebo vaccine, which was originally approved for the Ebola Zaire strain. This decision is driven by preliminary observations suggesting that individuals previously vaccinated against Ebola Zaire may exhibit some level of protection against Bundibugyo, particularly against severe or fatal outcomes. However, the definitive scientific evidence for this cross-protection in humans is still pending, necessitating urgent clinical trials.

Ervebo Trials

The immediate priority is to conduct rapid trials to ascertain Ervebo's efficacy against the Bundibugyo strain. Africa CDC scientists, including Professor Placide Mbala, anticipate the commencement of a phase 3 trial within weeks. This accelerated timeline follows a recommendation from the WHO's technical group, which, on July 31, prioritized Ervebo for large-scale evaluation in the absence of a readily available, specifically designed Bundibugyo vaccine. The primary objective of these trials is not to re-establish the vaccine's safety, which is already well-documented for Ebola Zaire, but to definitively measure its protective capacity against the Bundibugyo virus. A smaller cohort study is also planned to quickly gather initial data on cross-protection before expanding to larger-scale research. This dual-track approach aims to provide robust scientific evidence while simultaneously addressing the immediate public health crisis.

Jean-Jacques Muyembe's "Vaccine Curtain"

Adding another layer to the response strategy, Professor Jean-Jacques Muyembe, Director General of the National Institute of Biomedical Research (INRB) in the DRC, has proposed an innovative "vaccine curtain" approach. This strategy involves proactively vaccinating populations in provinces most vulnerable to the virus's spread, such as Tshopo and Haut-Uélé, to establish a protective barrier before the epidemic reaches new territories. This differs from the traditional "ring vaccination" method, which focuses on vaccinating contacts of confirmed cases and their contacts. Muyembe emphasizes that the "vaccine curtain" would function as a public health measure rather than a clinical trial, and he believes both strategies could be implemented concurrently. The goal is to create a broader, preventive shield, complementing the targeted response around known cases, thereby enhancing the overall containment efforts.

Vaccine Availability and Gavi

The feasibility of implementing such large-scale vaccination efforts hinges critically on the availability of vaccine doses. Currently, the DRC reportedly has approximately 2,000 doses of Ervebo. Globally, Africa CDC indicates a stock of 500,000 doses. To facilitate their deployment, Gavi, the Global Alliance for Vaccines and Immunization, has pledged to mobilize $40 million, contingent on the vaccine being recommended for this expanded use. The cost per dose is estimated at $98. While African officials are also engaging with the manufacturer, MSD, and other partners to bolster long-term vaccine production capabilities, particularly within Africa, these initiatives are not expected to provide an immediate solution for the current epidemic. The immediate challenge remains securing and deploying the existing global stock to meet the urgent needs of the affected regions in the DRC.