Ebola vaccines

Ebola disease is caused by a group of viruses called Orthoebolaviruses, and there are four species that are known to cause disease in humans. The four viruses are distinct genetically and a vaccine that is efficacious for one does not mean it will be efficacious for another: 

• Ebola virus (EBOV) causing Ebola virus disease (EVD, previously called Zaire ebolavirus)
• Bundibugyo virus (BDBV) causing Bundibugyo virus disease (BVD)
• Sudan virus (SUDV) causing Sudan virus disease (SVD)
• Taï Forest virus (TAFV) causing Taï Forest virus disease.

Currently, only one licensed and WHO prequalified vaccine (Ervebo) is available specifically for EBOV causing EVD. There are no licensed vaccines for the other species.

No. There is no licensed vaccine for Bundibugyo virus disease (BVD). Clinical trials are underway on new vaccine candidates designed specifically for the Bundibugyo virus and to determine whether Ervebo, the licensed vaccine against Ebola virus might also protect against the Bundibugyo virus.

Tumaini is a Phase 2/3 clinical trial of vaccine candidates against the Bundibugyo virus. The trial started in October 2026 in the Democratic Republic of the Congo. Tumaini, which means “hope” in Swahili, aims to generate evidence on the safety and efficacy of vaccine candidates against Bundibugyo virus, including Ervebo, which is currently the licensed vaccine for use against Ebola virus disease.

Tumaini is an adaptive platform trial designed to evaluate multiple vaccine candidates in parallel under a single protocol, which saves valuable time during an outbreak. Vaccine candidates are evaluated through a ring vaccination strategy, targeting contacts and potential contacts at highest risk of infection. The first vaccine candidate to enter the trial is Ervebo, and two vaccine candidates designed to protect against Bundibugyo virus have been selected by the WHO Technical Advisory Group on Candidate Vaccine Prioritization (TAG-CVP). The candidates include ChAdOx1 vector platform, developed by the University of Oxford with the Serum Institute of India, and mRNA-1469 developed by Moderna. 

Candidate vaccines are selected through an independent prioritization process led by the WHO TAG-CVP, ensuring that evaluation is guided by the best available scientific evidence and public health priorities.

The Ervebo vaccine is only recommended by WHO for use against Ebola virus disease (EVD). It is recommended for use in outbreaks and for preventive vaccination of health-care workers and frontline workers in areas at risk of future EVD outbreaks. Ervebo is safe and effective to protect against EVD.

July 2024 WHO recommendation on EVD vaccination

In case of an EVD outbreak, Ervebo vaccine can be accessed by countries through the International Coordinating Group (ICG) on Vaccine Provision global stockpile. More information.

Evidence from human sera of persons previously vaccinated with Ervebo and animal models suggests that Ervebo vaccine might offer some protection against disease and death from Bundibugyo virus. Nevertheless, there is currently insufficient evidence to determine whether Ervebo vaccine protects against Bundibugyo virus disease (BVD) in humans, or to quantify any potential level of protection.

Therefore, WHO’s Technical Advisory Group on Candidate Vaccine Prioritization recommended that Ervebo be assessed in a clinical trial to generate data on the protection against of BVD. WHO’s Strategic Advisory Group of Experts on Immunization (SAGE) also recommended that Ervebo should only be used within a research protocol and highlighted the urgency to generate robust evidence on vaccine efficacy against BVD through the Tumaini trial to inform future policy decisions to protect populations at risk. 

31 August 2026 WHO emergency guidance

SAGE meeting highlights October 2026

Both a ring vaccination randomized controlled trial (RCT) and an observational vaccine effectiveness (Obs-VE) study constitute research protocols. WHO considers a well-designed and well-conducted ring vaccination RCT to be the most rigorous and reliable approach for assessing the efficacy of Ervebo against Bundibugyo virus disease (BVD). Observational studies can  complement but not replace the need for evidence on vaccine efficacy from RCTs to inform future policy recommendations. However, WHO recognizes that in the context of a rapidly evolving BVD outbreak, countries facing substantial transmission may contemplate using Ervebo beyond a ring vaccination RCT. In such circumstances, where a ring RCT is not feasible, WHO recommends implementing vaccination within a carefully designed Obs-VE study to ensure the systematic generation of evidence on vaccine effectiveness of Ervebo against BVD.

Implementing Ervebo vaccination within a research protocol facilitates the systematic and high-quality documentation of vaccination activities and establishes predefined criteria for pausing, modifying, or discontinuing vaccination in response to emerging evidence on the level of protection that Ervebo may or may not provide against BVD.

Areas at risk of Ebola virus disease (EVD) outbreaks are likely to overlap with areas affected by the current Bundibugyo virus disease (BVD) outbreak. Ervebo vaccine is already recommended by WHO since 2024 to be used for health workers and frontline workers as a prevention measure for future EVD outbreaks. In the current situation where that use overlaps with the BDV outbreak, Ervebo vaccination of health and frontline workers can go ahead; however, its use should be implemented within the context of a research protocol, as possible.

In all instances of Ervebo use, especially outside a research protocol recipients should be clearly informed that the vaccine has only been proven to protect against EVD and this is the reason the vaccine is being offered. Recipients should also be advised to continue all recommended measures to protect themselves from BVD.

If Ervebo or another vaccine is shown to protect against Bundibugyo virus disease (BVD), WHO will provide policy guidance on how and when a vaccine should be used in BVD outbreak responses. The specific guidance will depend on the evidence available.

The Ervebo vaccine is licensed for use in individuals aged 12 months and older including pregnant and breastfeeding women during Ebola virus disease (EVD) outbreaks. In EVD outbreak settings, however, WHO recommends vaccination of all contacts and potential contacts identified in a ring, including children from birth.

Vaccination of children younger than 12 months is considered off-label use, meaning use of a vaccine outside the age group included in its approved indication.

People who survive Ebola virus disease (EVD) usually develop some protection against the disease. This protection is believed to last for several years, although it may slowly decrease over time.

EVD survivors are encouraged to apply all the protective measures against the disease, including vaccination.

Vaccination against Ebola virus disease (EVD) provides individual and collective immunity that reduces the harmful effects of the disease, including severe illness and death.

Unvaccinated persons have a high risk of dying in case of infection and increase the risk of the spread of the virus within the community.

It is important to ensure that all people at immediate risk of EVD are vaccinated to protect themselves and others.  

Most common side effects associated Ervebo vaccine are mild and occur within 24–48 hours of being vaccinated.

After receiving Ervebo, people can experience:

• injection site pain
• fever 
• headache.

Symptoms will generally disappear within 24 hours of onset.  

According to evidence, it takes between 10 and 14 days to develop a sufficient immune response against Ebola virus disease (EVD) that results in protection. This means that a person can still get infected and develop EVD before the vaccine provides protection.  

Vaccines are not 100% effective. The Ervebo vaccine reduces the risk of Ebola virus disease (EVD) which can cause severe illness and death. Not everyone develops the same level of protection after vaccination so some people may not be protected.

Because Ervebo is often given to people at highest risk of exposure during an EVD outbreak, some people may already have been infected with the virus before they received the vaccine, even if they do not yet have symptoms.

If a person was infected before vaccination, they may still develop EVD after receiving the vaccine. Anyone who develops symptoms of illness after vaccination should immediately seek medical care.

People who have received the vaccine should continue to follow public health advice and take steps to protect themselves and others from Ebola infection. They should avoid direct contact with someone who has or may have an Ebola infection including their body (dead or alive), or their body fluids, including blood, vomit, tears, saliva, urine or faeces, as well as their personal items such as bedding and clothes.  

No, it is not possible to be infected with Ebola virus as a result of vaccination. Ervebo contains only a small, non-infectious part of Ebola virus that helps the body's immune system recognize and respond to the virus in the future. It does not contain the complete Ebola virus which causes Ebola disease.

If someone develops Ebola disease after vaccination, it is most likely because they were infected before they received the vaccine or before the vaccine had enough time to provide protection.  

Antibodies to the virus have been detected up to five years after vaccination against Ebola virus disease (EVD). However, it is not known whether this level of antibodies is enough to protect against infection. Therefore, revaccination is recommended for anyone at high risk of the disease during an EVD outbreak if they have not received the Ervebo in the last six months. 

Research is ongoing to learn more about the need for booster doses.  

Control of an Ebola disease outbreak relies on a package of core public health interventions including:

• systematically engaging communities from the start in the Ebola disease response;
• early detection of confirmed and probable patients through active surveillance and contact tracing;
• functional laboratory services to confirm Ebola disease;
• isolate patients to prevent further spread at home or in the community and to provide safe and supportive care;
• ensuring adequate infection and prevention control measures to reduce transmission associated with care; and
• safely and respectfully burying deceased patients to reduce further spread of the virus through contact with deceased patients.

For more information see the WHO fact sheet on Ebola disease.

For Ebola virus disease, vaccination with Ervebo is an additional tool to help protect against the disease and control the transmission.  

For Bundibugyo virus disease (BVD), research is on-going to generate evidence on potential protection by BVD-specific candidate vaccines and to assess the potential protection of Ervebo vaccine against BVD.

Yes. Routine immunization should continue during an Ebola disease outbreak whenever it is safe to do so. Keeping routine immunization services running is an important part of maintaining essential health care.

If routine immunizations are interrupted, even for a short time, more people can become vulnerable to serious diseases such as measles, polio and diphtheria. These diseases can cause illness and deaths, particularly among babies and other vulnerable people.  

WHO has issued guidance to help health workers and the community safely continue routine vaccination services during the current Bundibugyo virus disease (BVD) outbreak. The guidance also provides key messages for communities about why routine vaccination remains important and how vaccination can be provided safely.

See August 2026 WHO’s guidance: Infection prevention and control considerations for routine immunization activities during the Bundibugyo virus disease outbreak: interim guidance, 21 August 2026.