Ebola virus disease (EVD), formerly known as Ebola hemorrhagic fever, is a severe, often fatal illness in humans. It is caused by the Ebola virus and was first identified in 1976 in the Democratic Republic of the Congo. Since then, several outbreaks have occurred, with the largest outbreak to date occurring in West Africa from 2014 to 2016. Vaccines have been developed to prevent Ebola virus disease, and in this article, we will discuss everything you need to know about these vaccines.
Are there Ebola Vaccines?
Yes, there are two licensed Ebola vaccines available.
The first vaccine, Ervebo, was licensed by the European Medicines Agency in November 2019 and prequalified by the World Health Organization (WHO). The United States Food and Drug Administration (FDA) licensed the vaccine in December 2019. Since then, several countries including Burundi, Central African Republic, the Democratic Republic of the Congo, Ghana, Guinea, Rwanda, Uganda, and Zambia have approved the vaccine.
Ervebo is safe and effective against the species Zaire ebolavirus, which is responsible for most outbreaks. The vaccine is recommended by the Strategic Advisory Group of Experts (SAGE) on Immunization as part of a broader set of Ebola outbreak response tools.
The second vaccine, Zabdeno (Ad26.ZEBOV) and Mvabea (MVA-BN-Filo), was recommended for marketing authorization by the European Medicines Agency in May 2020. This vaccine is delivered in two doses, with Zabdeno administered first, followed by Mvabea approximately eight weeks later. This prophylactic two-dose regimen is not suitable for an outbreak response where immediate protection is necessary.
For individuals at imminent risk of exposure to Ebola, such as healthcare professionals and those living in or visiting areas with an ongoing Ebola virus disease outbreak, who have completed the Zabdeno and Mvabea two-dose vaccination regimen, a Zabdeno booster vaccination should be considered if more than four months have passed since the second dose was administered.
Have these vaccines been used before?
Ervebo has been used under “expanded access” or “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 five 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 have been extrapolated from animal studies, and the exact level of protection provided by the vaccine regimen is not yet fully known.
Why are the vaccines not given to everyone at risk in endemic areas?
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 is available and 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 the 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 vaccines.
What are the side effects of the vaccine?
The Ervebo vaccine has been shown to be safe in clinical trials, with no serious adverse events reported. However, like all vaccines, the Ervebo vaccine can cause side effects. The most common side effects are pain and swelling at the injection site, fever, fatigue, headache, muscle pain, joint pain, and chills. These side effects are generally mild to moderate and resolve on their own within a few days.
The Zabdeno and Mvabea vaccine also has side effects, which were reported to be generally mild to moderate in severity. The most common side effects include pain and swelling at the injection site, fever, headache, fatigue, and muscle pain. These side effects usually resolve on their own within a few days.
It is important to note that the benefits of vaccination far outweigh the risks of side effects, and vaccination remains the most effective tool for preventing the spread of Ebola virus disease.
Ebola virus disease is a serious and often fatal illness that can have devastating consequences for individuals and communities. The development of effective vaccines against Ebola virus is a major milestone in the fight against this disease. Two vaccines, Ervebo and Zabdeno/Mvabea, have been licensed and are being used to protect individuals at risk of contracting Ebola virus disease, particularly during outbreaks.
While the vaccines are not yet available to everyone at risk in endemic areas, their availability and use in outbreak response have already saved many lives. As more data becomes available, we will learn more about the efficacy and safety of these vaccines and their potential use for broader preventive vaccination programs.
It is important to continue efforts to develop new and better vaccines and to ensure that those at highest risk of Ebola virus disease have access to the vaccines that are currently available. In addition, it is crucial to continue to invest in public health infrastructure, community engagement, and other measures to prevent the spread of Ebola virus disease and other infectious diseases.