Ebola vaccine

Ebola disease is caused by four different but closely related viruses, called Orthoebolaviruses. Ebola virus (also known as Zaire ebolavirus), Sudan virus, Bundibugyo virus, and Taï Forest virus.

The World Health Organisation (WHO) has recommended two Ebola vaccines. The first is the Ervebo vaccine. The second is the Zabdeno and Mvabea vaccine - these are two separate vaccines that are designed to be used together. They are given as two separate doses, approximately eight weeks apart.

Both have only been approved to provide protection against one of these viruses, the Zaire strain of Ebola virus. Of these, only the Ervebo vaccine is currently available, as the manufacturer of the Zabdeno and Mvabea vaccine combination is no longer marketing these vaccines.

They are all a type of vaccine called a viral vector vaccine. These vaccines use a harmless virus to deliver information about the disease, helping the body build protection against it.

In the case of Ebola, each recommended vaccine uses a different harmless virus to deliver information about a protein from the Ebola virus. After the vaccine, our cells then make the protein from the Ebola virus to educate our immune system so that it can recognise and help fight the virus if we come into contact with it in the future.

None of these vaccines can cause Ebola disease because they do not contain the whole Ebola virus. 

Ervebo is currently the only vaccine available for an outbreak response to Ebola virus disease (Zaire ebolavirus). When an outbreak is confirmed, countries can request Ervebo through the International Coordinating Group on Vaccine Provision.  

Vaccination is an important part of controlling an outbreak. The aim is to protect those at highest risk.

People who come into direct or indirect contact with a confirmed or probable case are usually eligible for a vaccine. This includes close friends, relatives and co-workers of suspected and confirmed cases, as well as frontline healthcare workers who are at high risk of infection whilst treating patients with Ebola.

In addition, anyone part of a response team who may come into contact with infected patients or contaminated objects, are also eligible for vaccination. This may include funeral staff, laboratory teams, contact tracing teams and drivers. 

The Ervebo, Zabdeno and Mvabea vaccines have been approved for use in individuals aged 1 year and older.

The Strategic Advisory Group of Experts on Immunisation (SAGE) recommends that, in an outbreak setting, countries should consider offering the Ervebo vaccine to those at higher risk of infection. This may include children from birth, as well as to pregnant and lactating women, even though these groups are not included in the vaccine’s official approval.

Those who have survived Ebola previously usually develop some protection against Ebola disease, but they should still continue taking protective measures against Ebola, which might include revaccination if recommended.

The most commonly reported side effects are injection site pain, headache, fatigue, muscle pain and fever. No major safety concerns have been identified in studies and outbreak use to date.      

Incidents of allergic reactions have been reported with Ervebo. Because one of the ingredients is produced using rice proteins, people with a severe allergic reaction to rice protein should not receive Ervebo.

People who have had a severe allergic reaction to chicken or eggs or an antibiotic known as gentamicin should not receive the Mvabea vaccine.

All vaccinated individuals should be observed for a minimum of 15 minutes post vaccination.

The WHO has a frequently asked questions page dedicated to the current approved licenced vaccine. 

The CDC has a resource page for healthcare professionals who want to know more about the Ervebo vaccine.

Ervebo

Ervebo contains a weakened, genetically modified virus that trains the immune system to recognise the Ebola virus, along with stabilising ingredients (human serum albumin, trometamol, water, hydrochloric acid and sodium hydroxide). It also contains trace amounts of rice protein and is produced using cell culture technology.

Summary of Product Characteristics

Zabdeno

Zabdeno contains a genetically modified chimpanzee adenovirus that teaches the immune system to recognise the Ebola virus. It also contains small amounts of ethanol, polysorbate 80, disodium edetate, histidine hydrochloride monohydrate, sodium chloride, sucrose, water and sodium hydroxide.

Summary of Product Characteristics

Mvabea

Mvabea contains a genetically modified virus that carries proteins from the Ebola virus (Zaire ebolavirus), Sudan ebolavirus, Tai Forest ebolavirus, and Marburg virus. It also contains sodium chloride, trometamol, water and hydrochloric acid to help maintain the vaccine’s stability as well as trace amounts of chicken or egg proteins and gentamicin from the manufacturing process.

Summary of Product Characteristics 

Ervebo vaccine

This vaccine provides rapid protection following a single dose and is recommended for use when there is an Ebola outbreak. A study based on a vaccine trial conducted during an outbreak in West Africa, found that no vaccinated people developed Ebola disease 10 or more days after receiving the vaccine. This suggests the vaccine is highly protective once the body has had time to develop an immune response.  

Ervebo uses a modified animal virus called vesicular stomatitis virus (VSV), which has been altered to carry a protein from the Ebola virus, which helps the body develop protection.

Supplies of Ervebo are kept in a global vaccine stockpile, ensuring they can be sent quickly to areas affected by an outbreak in a co-ordinated and equitable way.

Zabdeno and Mvabea vaccine

These are two separate vaccines that are designed to be used together. They are given as two separate doses, approximately eight weeks apart.

Zabdeno uses a harmless modified adenovirus (called Ad26) to carry information from the Ebola virus. This information allows the body to make an Ebola protein, helping the immune system learn to recognise and fight Ebola.

Mvabea is also a viral vector vaccine, but it uses a different harmless virus (MVA-BN). This modified virus carries information that allows the body to make proteins from several viruses, including the Ebola virus, Sudan virus and Taï Forest virus and Marburg virus.

This vaccine combination has been recommended for preventative vaccination in areas of lower risk for Ebola, or areas neighbouring outbreaks, as the two-dose regime takes longer to provide protection from the Ebola virus. Studies have shown that this combination of vaccines can stimulate an immune response that should be protective against the Ebola virus. However, there is less information about how effective it is, because it is not used in outbreak settings.

There are a number of different vaccines currently under development to protect against other viruses that cause Ebola disease.

WHO and CEPI are working with a number of partners globally, including the University of Oxford, to support and accelerate the response to the 2026 Ebola disease outbreak caused by the Bundibugyo virus. 

Vaccination strategies 

Following an outbreak of Ebola virus disease, a ring vaccination strategy may be used to try to contain the outbreak. This involves vaccinating close contacts and potential contacts of confirmed or probable cases, and may also be extended to contacts of contacts too.  

A contact is someone who has been exposed to potentially infected body fluids or objects contaminated with them. Potential contacts include family members, extended family members, neighbours living near the contacts, and all the household members of contacts. This strategy creates a ‘ring of immunity’ (protection) around a confirmed or probable case. 

Targeted geographical vaccination is another possibility. This is where a whole village or neighbourhood is vaccinated, rather than just the known and potential contacts. This method is used when it is hard to trace contacts for logistical or safety reasons, or if the cases are all clustered close together.

Pregnancy and Breastfeeding

To save the lives of mothers and their babies, reduce complications, and limit the spread of disease, recommendations must be made on the prevention, treatment, and surveillance of women who are exposed to Ebola during pregnancy or breastfeeding, or who survive Ebola disease with ongoing pregnancies. The WHO has produced guidance on the management of pregnant and breastfeeding women in the context of Ebola virus disease. 

Infection post-vaccination

Not everybody responds to the vaccines in the same way, and they do not protect everyone from infection. Additionally, some people may have become infected before they received the vaccine. Therefore, it should not be assumed that just because someone has been vaccinated, they cannot be infected.

Whilst studies have shown that the immune response post vaccination can last for a few years, it is not known what level of antibodies is required to protect against Ebola infection. Therefore, revaccination is currently recommended for anyone at high risk who has not had an Ebola vaccine within the previous 6 months. Research is currently ongoing to determine how effective it is to use a different Ebola vaccine for revaccination.