Vaccines against Ebola exist, but not against the strain of the current epidemic
A decade after Ebola vaccines changed the outbreak response, a new outbreak in central Africa is being driven by a strain the world never really prepared for.
By Paul Adepoju edited by Lewis asked.
A nurse wearing protective medical clothing draws a dose from a vaccine vial during the launch of an experimental Ebola vaccination campaign at Mulago Referral Hospital during a previous Ebola outbreak in Kampala, Uganda, February 3, 2025.
BADRU KATUMBA/AFP via Getty Images
According to health officials, approximately 50 confirmed Ebola cases, 600 suspected cases and 130 suspected deaths are currently under investigation in the Democratic Republic of Congo (DRC) and Uganda. race to contain a rapidly expanding epidemic caused by the rare Bundibugyo species of Ebola virus. Cases have also been detected in the main Congolese cities of Goma and Bunia, raising fears of wider spread.
Experts are working on several Bundibugyo vaccine candidates, including an mRNA vaccine, but they are not yet available.
“This species of Ebola is a species for which there is no approved vaccine or treatment,” said Anne Ancia, the World Health Organization representative in the DRC. said during a press briefing on Tuesday.
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There is six known species of the Ebola virusfour of which are known to cause disease in humans. But Bundibugyo virus has historically caused relatively few outbreaks and has remained a lower research priority compared to the more deadly Zaire strain or even Marburg virus, which is in the same viral family as Ebola.
“Most Ebola control measures have focused on Ebola Zaire, which was traditionally the deadliest strain and has historically been the most common strain causing outbreaks,” says Amesh Adaljasenior scholar at the Johns Hopkins Center for Health Security. “This also means that many other strains of Ebola have not necessarily benefited from the same level of vaccine development. »
“Ideally what you would want is some sort of universal filovirus [the family that contains Ebola and Marburg viruses] vaccine which acts against all strains of Ebola, as well as against Marburg strains. I think that would be the holy grail here.
Consider mRNA Vaccines
The outbreak has reignited interest in mRNA vaccines, which has transformed the global response to COVID.
Shanelle Hall, senior advisor to the director general of the Africa Centers for Disease Control and Prevention for management and operations, told a press briefing that experimental vaccines and treatments against the Bundibugyo strain, including the monoclonal antibody DP134 and remdesivir-based treatments, are being considered for use in randomized controlled trial protocols in the DRC and Uganda, although none have yet started.
The agency is also reviewing several vaccine candidates, including the live non-mRNA vaccine Ervebo, which was used during the Ebola outbreaks in Zaire, alongside early-stage Bundibugyo-focused candidates from Moderna, the University of Oxford and the International AIDS Vaccine Initiative. The inclusion of Moderna’s vaccine among the candidates being considered has also renewed attention on whether mRNA technologies could eventually help fill long-standing gaps in preparedness for rarer species of Ebola. “Scientists are looking at them to develop accelerated plans and then protocols to assess the effectiveness of cross-protection between strains,” she says.
Regarding mRNA vaccines, Adalja says that “because of the speed with which they can be made and adapted, these should be at the top of the list when thinking about developing vaccines against emerging pathogens like Ebola strains for which we don’t have vaccines.”
The Coalition for Epidemic Preparedness Innovations (CEPI), a nonprofit organization that funds vaccine development, said it is evaluating vaccine and antibody candidates that could potentially be evaluated during the outbreak. “Currently, there is no vaccine candidate specific to Bundibugyo in phase 1. [early-stage] clinical trials, but several are in preclinical development [animal studies]” said Nicole Lurie, CEPI’s executive director for preparedness and response, in a statement.
CEPI said it has activated an internal emergency response team to coordinate scientific, financing and vaccine development efforts related to the outbreak. It is also exploring ways to rapidly advance vaccine candidates and identify manufacturers capable of producing doses for clinical trials against the current outbreak.
Public health experts have also called for a broader “prototype pathogen” or viral family approach to preparedness, in which scientists develop countermeasures targeting “conserved” characteristics shared by related viruses rather than focusing on one strain at a time. “I’m someone who has been advocating a viral family approach for a while. Think about the viral family as a whole,” says Adalja.
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