Ebola virus disease: Vaccines

Yes, there are 2 licensed Ebola vaccines.

Ervebo was licensed in November 2019 by the European Medicines Agency and prequalified by WHO. The United States Food and Drug Administration licensed the vaccine in December 2019. Since then Burundi, Central African Republic, the Democratic Republic of the Congo, Ghana, Guinea, Rwanda, Uganda and Zambia have also approved the vaccine.

The vaccine is safe and protective against the species Zaire ebolavirus. It is recommended by the Strategic Advisory Group of Experts (SAGE) on Immunization as part as a broader set of Ebola outbreak response tools.

In May 2020, the European Medicines Agency recommended to grant marketing authorisation to a second new vaccine delivered in 2 doses called Zabdeno (Ad26.ZEBOV) and Mvabea (MVA-BN-Filo) for individuals 1 year and older.

The vaccine is delivered in 2 doses: Zabdeno is administered first and Mvabea is given approximately 8 weeks later as a second dose. This prophylactic 2-dose regimen is therefore not suitable for an outbreak response where immediate protection is necessary.

For individuals at imminent risk of exposure to Ebola (for example, health care professionals and those living in or visiting areas with an ongoing Ebola virus disease outbreak) who completed the Zabdeno and Mvabea 2-dose vaccination regimen, a Zabdeno booster vaccination should be considered if more than 4 months have passed since the second dose was administered.

The Ervebo vaccine has been used under “expanded access” or what is also known as “compassionate use” for 16 000 people in Guinea in 2015 and for 345 000 people during the 2018-2020 outbreaks in the Democratic Republic of the Congo.

The Zabdeno and Mvabea vaccine was studied in a total of 3 367 adults, adolescents and children who participated in 5 clinical studies conducted in Europe, Africa and the United States of America. These studies demonstrated that the vaccine regimen is safe and could induce an immune response against the Ebola virus. Efficacy data in humans has been extrapolated from animal studies. The exact level of protection provided by the vaccine regimen is not yet fully known.

As Ebola outbreaks are relatively rare and unpredictable in nature, and due to limited vaccine quantities, the Ervebo vaccine is reserved for outbreak response to protect persons at the highest risk of contracting Ebola virus disease under a “ring vaccination” strategy, which is similar to the approach used to eradicate smallpox.

A global stockpile will be available starting in January 2021 and will be managed through the International Coordinating Group (ICG) on Vaccine Provision. As is currently the case for stockpiles of cholera, meningitis and yellow fever vaccines, the ICG will be the decision-making body for allocation of the vaccine.

The Strategic Advisory Group of Experts (SAGE) on Immunization is currently reviewing the available evidence on Ervebo and Zabdeno and Mvabea vaccine and is expected to issue policy recommendations for preventive use in 2021.

The Ervebo vaccine is to be used during an outbreak to protect persons at the highest risk of contracting Ebola virus disease under a “ring vaccination” strategy and as per the recommendation of the manufacturer.

The Ervebo vaccine is indicated for use for adults over 18 years of age, not including pregnant and lactating women.

However, during the 2018-2020 outbreak in Ituri, North Kivu and South Kivu in the Democratic Republic of the Congo, the vaccine was used as recommended by the Strategic Advisory Group of Experts (SAGE) on Immunization in children over 6 months old and in pregnant and lactating women under a compassionate use clinical protocol. The Strategic Advisory Group of Experts (SAGE) on Immunization is reviewing the safety data for the use of this vaccine in these populations and further recommendations are expected in early 2021.

The Zabdeno and Mvabea vaccine regimen is indicated for immunisation in individuals over 1 year of age.

In vaccine studies conducted since 2015, most of the adverse effects were typically mild. Vaccinated individuals most commonly reported headache, fatigue, muscle pain and mild fever.

No vaccine is 100 percent effective. Persons who receive the vaccine should continue to protect themselves from Ebola virus infection by not touching a patient’s body (dead or alive), or bodily fluids, including blood, vomit, saliva, urine or faeces. Personal items used by the patient like bedding and clothes may also be contaminated with Ebola virus and should be avoided.

If a person receiving the vaccine was already infected with the Ebola virus before he/she was vaccinated, they could develop Ebola virus disease after they receive the vaccine. If they develop any symptom of illness, they should immediately contact the vaccination team.

No, the vaccines do not contain live virus and it is not possible to be infected with Ebola as a result of vaccination.

Ring vaccination is a strategy to vaccinate individuals at highest risk of infection due to their connection to a patient confirmed with the virus.

When a patient is laboratory confirmed, the definition of the vaccination ring is made as follow:

• Contacts are defined as individuals who, in the last 21 days, lived in the same household, were visited by the patient after they developed symptoms, or visited the patient or were in close physical contact with the patient's body, body fluids, linen or clothes.
• Contacts of contacts are defined as neighbours, family, or extended family members at the closest geographic boundary of all contacts, plus household members of all contacts who do not live in the same locality as the patient.
• SAGE also recommends vaccinating health care workers and frontline workers responding to the outbreak who may be in contact with Ebola patients.

The ring is not necessarily a contiguous geographic area but captures a social network of individuals and locations that may include dwellings or workplaces further afield where the index patient spent time while symptomatic, or the households of individuals who had contact with the patient during the illness or after his or her death. Experience suggests that each ring may be composed of an average of 150 persons.

Each vaccination team is trained and knowledgeable on vaccination practices against Ebola.

The steps for the ring vaccination using Ervebo are clearly defined. These include:

• The ring vaccination team leader and a trained local social mobilizer visit the family and the neighbours of the Ebola patient and explain the vaccination process and why they are eligible for vaccination.
• The definition of the ring is made by 2 trained members of the vaccination team who list all of the contacts and contacts of contacts of a confirmed Ebola case (deceased or alive), including persons who may not be present in the community at the time of the visit of the ring definition team.

The use of a vaccine is one of the several components of the strategy to control an Ebola outbreak. Other important components include:

• Early detection of new Ebola infections through close monitoring of contacts;
• Functional laboratory services to confirm Ebola infections;
• Separating (isolating) patients to prevent further spread at home or in the community and to provide safe and supportive care;
• Safely and respectfully burying the dead to reduce further spread of Ebola virus through contact with deceased patients;
• Systematically engaging communities in the Ebola response.

The Strategic Advisory Group of Experts (SAGE) on Immunization is reviewing the emerging clinical data from the people vaccinated since 2015 to determine how long the vaccine protects a person from Ebola virus infection. A recommendation for preventive use is expected in 2021.