In Africa, patients with hemorrhagic fever infected with the Ebola virus are increasing at an unprecedented pace. In the past, only dozens were infected in the first 100 days of an outbreak, but this time more than 200 cases have emerged, shocking the medical community. A vaccine was developed for the virus that fueled earlier Ebola outbreaks, but there is still no vaccine for the current virus, leaving no way to prevent it.
The medical community is accelerating development of a new Ebola vaccine to prevent a catastrophic outbreak. U.S. and U.K. researchers are each developing vaccines that induce an immune response to the Ebola virus using different viruses. China developed a vaccine that directly delivers genes from the Ebola virus. They confirmed that it protects not only against the virus that circulated before, but also the virus behind the current crisis.
◇Same approach as the coronavirus mRNA Vaccine
Researchers at the Wuhan Institute of Virology in China said in a paper published on the 18th in the Proceedings of the National Academy of Sciences (PNAS) that "mouse experiments confirmed that a messenger ribonucleic acid (mRNA) vaccine provides immunity against the Ebola virus."
Ebola hemorrhagic fever is a severe infectious disease caused by the Ebola virus that begins with headache, muscle pain, fever, and general fatigue, followed by bleeding throughout the body. The virus was first discovered in 1976 near the Ebola River in the Democratic Republic of the Congo (DR Congo), which gave the disease its name. It spreads through contact with blood or bodily fluids, and the fatality rate averages around 50%. In some situations it reaches as high as 90%.
The vaccine developed by Chinese researchers works on the same principle as the coronavirus vaccines developed separately by Pfizer and Moderna in the United States during the COVID-19 pandemic. Instead of injecting the virus directly, it induces an immune response by delivering mRNA containing genetic information. The researchers encapsulated mRNA that makes the Ebola virus's surface glycoprotein, used to enter human cells, and its nucleoprotein, which protects genetic material inside cells, in lipid nanoparticles and injected it into mice. When the mRNA synthesizes viral proteins, antibodies and immune cells that counter them are induced.
In particular, the Chinese team said mouse experiments showed the mRNA Vaccine had preventive effects against all three Ebola viruses. The genus Ebolavirus comprises six species. Of these, four—Zaire (EBOV), Sudan (SUDV), Bundibugyo (BDBV), and Tai Forest (TAFV)—cause severe hemorrhagic fever in humans. The current outbreak is driven by the Bundibugyo species.
While each Ebola virus has a different surface glycoprotein, the nucleoprotein is nearly the same. The Chinese researchers combined mRNAs for the glycoproteins of the Zaire, Sudan, and Bundibugyo viruses with mRNA for the shared nucleoprotein to boost immunity. The scientific community sees the mRNA Vaccine as an original strategy that prevents multiple Ebola viruses at once, but says it must show the same efficacy in monkeys, fellow primates to humans, to raise its chances of success.
◇Inserting Ebola genes into other viruses
According to the WHO, more than 11,300 people died of Ebola in West Africa in 2014. It was the worst outbreak since the Ebola virus was discovered. More than 500 health workers also died. The cause was the Zaire Ebola virus. All vaccines currently available for Ebola provide immunity only against the Zaire Ebola virus.
Ervebo, an Ebola vaccine developed by Merck (MSD), was approved by the U.S. Food and Drug Administration (FDA) in 2019 for use in adults 18 and older, and in 2023 the indication was expanded to those 12 months and older. The two-dose heterologous regimen of Zabdeno and Mvabea, developed by Janssen, a subsidiary of Johnson & Johnson (J&J), was approved by the European Medicines Agency (EMA) in 2020.
U.S. and U.K. researchers are developing a Bundibugyo vaccine using the same approach as the Zaire Ebola vaccine. The method uses another virus as a gene delivery vehicle, or vector. When the vector virus produces the Ebola virus's glycoprotein in the body, a matching immune response is induced.
Thomas Geisbert of the University of Texas Medical Branch inserted the gene for the Bundibugyo Ebola virus glycoprotein into the vesicular stomatitis virus. In monkey studies, the vaccine blocked Bundibugyo Ebola. Geisbert was a key developer of Merck's Ervebo vaccine. Vesicular stomatitis virus is harmless to humans, so its replication does not need to be blocked. That allows abundant production of the Ebola protein and a rapid immune response.
The Oxford Vaccine Group used an adenovirus that causes the common cold as the vector. This is the same approach used in the COVID-19 vaccine from the British drugmaker AstraZeneca. It likewise induces an immune response by synthesizing the Ebola virus glycoprotein in the body. The common cold virus is also recognized by the body as a pathogen. To avoid confusing the immune response, the researchers used a chimpanzee virus as the vector instead of a human one. For the same reason, they also blocked replication of the vector virus. Oxford said it is preparing production with the Serum Institute of India, the world's largest vaccine manufacturer.
◇Spreading at record speed, raising concern
For now, the chances of Ebola spreading worldwide are slim. It is transmitted through contact with blood or bodily fluids, not through the respiratory route like COVID-19. Drugmakers have not actively developed vaccines because Ebola outbreaks have been limited to Africa. Scientists are concerned that this Ebola is different. The rise in patients is unusually sharp.
On the 15th, the governments of DR Congo and Uganda officially declared an Ebola outbreak, reporting 246 suspected infections and 80 deaths. But three days later, researchers at Imperial College London (ICL) published findings suggesting the actual number of infections could be much higher.
Earlier Ebola outbreaks had only dozens of patients at the time of the official declaration, but this year there were already 246. For example, in Mar. 2014, the Guinean government officially declared an Ebola outbreak and reported only 49 suspected cases and 29 deaths. U.K. researchers said that comparing past Bundibugyo Ebola fatality rates to current reported figures suggests infections may have already surpassed 1,000. Ebola infections and deaths are continuing to rise. On the 23rd, the DR Congo government said there were 867 suspected Ebola cases, of which 204 had died.
Geisbert of the University of Texas Medical Branch stressed the need to speed development of a Bundibugyo Ebola vaccine. In an interview with AFP, he said, "Ebola vaccines are not a money-making business, so there was no incentive for big pharmaceutical companies to jump in," adding, "I published research on a Bundibugyo vaccine candidate in 2013, but the work was left unattended afterward."
Geisbert said the situation was similar when he first reported in 2005 the results that would later become the Ervebo Ebola vaccine. "Only after the massive West African Ebola outbreak in 2014, which claimed more than 11,300 lives, did attention finally turn to vaccines," he said. "If we start right now, a Bundibugyo vaccine is possible in six to seven months."
References
PNAS (2026), DOI: https://doi.org/10.1073/pnas.2517814123
Imperial College London (2026), DOI: https://doi.org/10.25560/13005307
PLOS Neglected Tropical Diseases (2013), https://www.imperial.ac.uk/mrc-global-infectious-disease-analysis/research-themes/preparedness-and-response-to-emerging-threats/report-ebola-update-20-05-2026/