In Africa, cases of hemorrhagic fever patients infected with the Ebola virus are rising 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 occurred, shocking the medical community. A vaccine was developed for the virus that caused 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 infection crisis. U.S. and U.K. researchers are developing vaccines that induce immune responses to the Ebola virus using different viruses. China has developed a vaccine that directly injects Ebola virus genes. It confirmed preventive effects not only against viruses that spread in the past but also against the virus driving the current situation.
◇ Same approach as the COVID 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. It begins with headache, muscle pain, fever, and general fatigue, and later causes bleeding throughout the body. The virus was first discovered in 1976 near the Ebola River in the Democratic Republic of Congo (Democratic Congo), which gave it its name. It is transmitted through contact with blood or bodily fluids, and the fatality rate is around 50% on average. In some situations, it can reach as high as 90%.
The vaccine developed by Chinese researchers uses the same principle as the COVID-19 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 produces the surface glycoprotein the Ebola virus uses to enter the human body, along with nucleoprotein that protects genetic material inside the cell, in lipid nanoparticles and injected it into mice. When the mRNA synthesizes the viral proteins, antibodies and immune cells that counter them are induced.
In particular, the Chinese team said the mRNA Vaccine showed preventive effects against all three Ebola viruses in mouse experiments. The genus Ebolavirus consists of six species. Of these, four—Zaire (EBOV), Sudan (SUDV), Bundibugyo (BDBV), and Taï Forest (TAFV)—cause severe hemorrhagic fever in humans. The current outbreak is driven by the Bundibugyo species.
Each Ebola virus has a different surface glycoprotein, but the nucleoprotein is nearly identical. The Chinese researchers combined mRNA for the glycoproteins of the Zaire, Sudan, and Bundibugyo viruses with mRNA for the nucleoprotein they share to boost immune effects. Scientists view the mRNA Vaccine as an innovative approach that prevents multiple Ebola viruses simultaneously, but say it must show the same efficacy in monkeys, primates like humans, to raise the likelihood 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 medical workers also died. The cause was the Zaire Ebola virus. All currently available Ebola vaccines provide immunity only against the Zaire Ebola virus.
Ervebo, the 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 genetic delivery vehicle, or vector. When the vector virus produces the Ebola virus glycoprotein in the body, it induces a matching immune response.
Thomas Geisbert of the University of Texas Medical Branch inserted the glycoprotein gene of the Bundibugyo Ebola virus into vesicular stomatitis virus. In monkey studies, this vaccine blocked Bundibugyo Ebola. Geisbert was a key developer of Merck's Ervebo vaccine. Vesicular stomatitis virus is harmless to humans, so it does not need to be replication-deficient. That allows robust production of the Ebola protein and can trigger an immune response quickly.
The Oxford Vaccine Group used an adenovirus that causes the common cold as a vector. It is the same approach used in the COVID-19 vaccine by U.K. 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 India's Serum Institute, the world's largest vaccine manufacturer.
◇ Spreading at record speed, raising concerns
For now, the chance of Ebola spreading worldwide is slim. It is transmitted through blood or bodily fluids and does not spread through the respiratory route like COVID-19. Drugmakers have not actively pursued vaccine development because Ebola outbreaks have been confined to Africa. Scientists are concerned that this Ebola is different from before. The pace of increase in patients is unusual.
On the 15th, the governments of Democratic Congo and Uganda announced 246 suspected Ebola cases and 80 deaths, officially declaring an Ebola outbreak. Three days later, researchers at Imperial College London (ICL) released findings suggesting the actual number of infections could be far higher.
In previous Ebola outbreaks, only dozens of patients were recorded at the time of the official declaration, but this year the figure was already 246. For example, in Mar. 2014, the Guinea government officially declared an Ebola outbreak, reporting only 49 suspected cases and 29 deaths. The U.K. researchers said that comparing past Bundibugyo Ebola fatality rates with current reported figures suggests infections may already have surpassed 1,000. Ebola cases and deaths are continuing to rise. On the 23rd, the Democratic Congo government said there were 867 suspected Ebola patients, of whom 204 had died.
Geisbert of the University of Texas Medical Branch stressed that development of a Bundibugyo Ebola vaccine must be accelerated. In an interview with AFP, Geisbert said, "Ebola vaccines are not a money-making business, so there has been no incentive for big pharmaceutical companies to jump in," and added, "We published research on a Bundibugyo vaccine candidate in 2013, but the work was left idle after that."
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 unprecedented Ebola outbreak in West Africa in 2014, which claimed more than 11,300 lives, did attention begin to focus on 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), https://www.imperial.ac.uk/mrc-global-infectious-disease-analysis/research-themes/preparedness-and-response-to-emerging-threats/report-ebola-update-20-05-2026/
PLOS Neglected Tropical Diseases (2013), DOI: https://doi.org/10.1371/journal.pntd.0002600