Ebola Overview

What is Ebola?

Ebola is a serious contagious viral disease with a high mortality rate.  The natural reservoir for the virus is thought to be a fruit bat native to Africa. Both humans and non-human primates are susceptible to infection.  The disease was initially discovered in 1976 after two separate outbreaks of hemorrhagic fever occurred in different areas of Central Africa. The first occurred in the Democratic Republic of Congo, near the Ebola River, and the second occurred approximately 500 miles away, in South Sudan. 

Ebola virus and Marburgvirus belong to the family Filoviridae and cause suppression of innate and adaptive immune responses that lead to a syndrome resembling septic shock.  Six species of Ebola virus (Zaire, Sudan, Ivory Coast, Bundibugyo Reston, and Bombali) have been identified with four confirmed to be infectious in humans. The Reston species can cause disease in pigs and nonhuman primates but not humans. It is not yet known if the newly discovered Bombali species can cause disease in humans.  The largest Ebola outbreak began in 2014 in Southeastern Guinea and was caused by the Zaire ebolavirus. 

Symptoms start with a fever, headache, muscle and stomach pain, diarrhea, vomiting, fatigue, weakness, skin bruising and bleeding. As the disease progresses, damage to the immune system as well as the body’s internal organs occur. White blood cell and platelet counts decrease and both internal and external bleeding can occur. Fatality rates from the disease have ranged from 25 to 90 percent but the average case fatality rate is estimated at 50 percent.    A person can have the virus but not show any symptoms for as long as three weeks. 

Persons who survive Ebola virus disease develop long-term immunity; however, health problems frequently persist upon recovery. Common symptoms include fatigue, headaches, weight gain, vision disturbances, joint and muscle pain, loss of appetite, and stomach pain. Additional long-term health issues can also include dry mouth, neck swelling, tightness of the chest, hearing problems, memory problems, tingling and pain in the hands and feet, changes in menstruation, impotence, inflammation of the testicles, decreased sex drive, sleep disturbances, inflammation of the tissues surrounding the heart, anxiety, depression, and post-traumatic stress disorder. 

Individuals who survive can still have the virus in their system for weeks to months afterward.  In certain instances, persons who recover from Ebola can harbor the virus for several years, and even spread it on to others. In 2016, researchers discovered that an Ebola survivor transmitted the virus through sexual contact approximately 470 days after exhibiting initial symptoms of disease. This transmission was linked to several cases of disease in Liberia and Guinea. 

Scientists investigating the 2021 Ebola virus outbreak in Guinea discovered that the source of the outbreak was likely a survivor of the 2014-2016 West Africa Outbreak. This hypothesis was reached after a genetic analysis revealed that the virus sequence from the current outbreak was closely related to the 2014-2016 West Africa Ebola virus strain. 

Is Ebola contagious?

Ebola virus is contagious and is spread through inhalation, ingestion and/or passage through breaks in the skin when an uninfected person comes in contact with the body fluids (blood, saliva, nasal secretions, stool, vomit, breastmilk, semen, urine, tears) of an infected person or the cadaver of a person who died from Ebola.  Ebola is also spread when a person comes in contact with bandages, clothes, or other objects that have been contaminated with body fluids, especially blood, of an infected person.   

Depending upon the body fluid, Ebola virus has been detected in body fluids from six to 40 days after disease onset, including during the convalescent stage.  A small percentage of persons who recover from Ebola have been found to have the virus present in bodily fluids for longer than nine months. 

Ebola can also be spread through sexual contact, and men who recover from the disease are advised to practice safe sex for at least one year after the onset of symptoms or until their semen has tested negative for Ebola virus on two separate occasions. 

After coming in contact with someone infected with Ebola, the incubation period from initial exposure to onset of acute disease symptoms is between 2 and 21 days, with an average of 8 to 10 days.   

There is some evidence that Ebola may be spread when an infected person coughs or sneezes into the air, but there is disagreement among scientists and public health officials on whether airborne transmission does occur.        A person with Ebola virus is only contagious to others after they begin to show signs of illness. 

Those who recover from Ebola virus infection may develop antibodies lasting 10 years or longer, but it is not known if they can become immune for life or if they are susceptible to infection from different strains of Ebola virus.  A person remains infectious until the virus is no longer found in their blood. 

In certain instances, persons who recover from Ebola can harbor the virus for several years, and even spread it on to others. In 2016, researchers discovered that an Ebola survivor transmitted the virus through sexual contact approximately 470 days after exhibiting symptoms of the disease. This transmission was linked to several cases in Liberia and Guinea. 

Scientists investigating the 2021 Ebola virus outbreak in Guinea discovered that the source of the outbreak was likely a survivor of the 2014-2016 West Africa Outbreak. This hypothesis was reached after a genetic analysis revealed that the virus sequence from this outbreak was closely related to the 2014-2016 West Africa Ebola virus strain. 

What is the history of Ebola in America and other countries?

The first Filovirus (Marburg) was identified in 1967 when about 30 laboratory workers in Germany and Yugoslavia developed hemorrhagic fever and seven died. The workers had handled kidney tissues from infected African green monkeys imported from Uganda when they were preparing primary cell cultures for polio vaccine production. 

Ebola virus disease was initially discovered in 1976 after two separate outbreaks of hemorrhagic fever occurred in different areas of Central Africa. The first occurred in the Democratic Republic of Congo, near the Ebola River, and the second occurred approximately 500 miles away in South Sudan. 

Outbreaks of Ebola were sporadic and primarily confined to Africa until a large outbreak originating in Southeast Guinea began in March 2014. Most cases occurred in Guinea, Liberia, and Sierra Leone, but cases were also detected in the Democratic Republic of Congo, Italy, Mali, Nigeria, Senegal, Spain, United Kingdom, and the United States.  There were 28,616 confirmed, probable, and suspected cases and 11,310 deaths in Guinea, Liberia, and Sierra Leone. An additional 36 cases and 15 deaths occurred when the outbreak spread outside these three countries. The World Health Organization (WHO) ended the Ebola virus public health emergency on March 29, 2016. 

In August 2018, health officials from the Democratic Republic of Congo (DRC) reported that an outbreak of Ebola virus disease had occurred in the North Kivu province. WHO declared an end to this outbreak on June 25, 2020. A total of 3,470 cases and 2,287 deaths were linked to this outbreak.  An additional outbreak was declared on June 1, 2020 in the Mbandaka, Equateur Province of western DRC. There were 130 cases and 55 deaths associated with this outbreak. The outbreak was declared over on November 18, 2020. 

On February 7, 2021, officials from the DRC announced that an outbreak of Ebola virus had occurred in the North Kivu Province. According to health officials, a female presented with symptoms of illness in late January and died on February 4, 2021.  One week later, health officials in Guinea reported an outbreak of Ebola virus disease had occurred for the first time since 2016. The initial case was believed to have originated in a nurse who infected five family members and a traditional practitioner whom she consulted for assistance. Five of the seven cases were fatal.  This outbreak was declared over in May 2021.

Another outbreak in the DRC occurred between October and December 2021, with 11 reported cases and 6 associated deaths. Health officials believe this outbreak was caused by an Ebola virus survivor with a persistent infection. 

Can Ebola cause injury and/or death?

Ebola virus is a serious illness that is highly fatal. Symptoms start with a fever, headache, muscle and stomach pain, diarrhea, vomiting, skin bruising and may also include a skin rash, red eyes, and hiccups.  Additional symptoms may include shortness of breath, chest pain, confusion, seizures, and bleeding. Fatal cases usually present with more severe symptoms early in the course of the illness, and death generally occurs from sepsis or multiorgan failure between days 6 and 16. 

Historically, between 25 and 90 percent of Ebola cases have ended in death, with the average case fatality rate estimated at 50 percent.  The Africa-based outbreak that began in Guinea, Liberia, and Sierra Leone in 2014 affected 28,616 individuals and resulted in 11,310 deaths. The outbreak also spread outside these three countries and infected 36 individuals and caused 15 deaths. 

Persons who survive Ebola virus disease frequently experience long-term health problems which may include fatigue, headaches, weight gain, vision disturbances, joint and muscle pain, loss of appetite, and stomach pain. Additional health problems can also include dry mouth, neck swelling, tightness of the chest, hearing problems, memory problems, tingling and pain in the hands and feet, changes in menstruation, impotence, inflammation of the testicles, decreased sex drive, sleep disturbances, inflammation of the tissues surrounding the heart, anxiety, depression, and post-traumatic stress disorder. 

Who is at highest risk for getting Ebola?

Ebola virus disease primarily occurs in sub-Saharan Africa.  When an outbreak occurs, persons most at risk for developing illness include healthcare providers, close contacts or family members of infected individuals, and any person who may come into contact with the remains of persons who have died from the disease. 

Health care workers are at high risk of disease if they do not have the personal protective equipment needed to protect themselves from illness or do not apply correct infection control techniques when caring for an infected individual. Persons responsible for handling the remains of persons who have died from Ebola are at high risk of infection since the level of virus remains high after death. Special training and the use of personal protective equipment can reduce the risk of infection. 

Who is at highest risk for suffering complications from Ebola?

Younger children and older adults are at a higher risk of death from Ebola virus disease. The highest fatality rates are in children under the age of five years and especially among those under 12 months of age.¹

Can Ebola be prevented and are there treatment options?

Ebola is a fragile virus and is readily killed by soap and water, bleach, or other products such as hospital-grade quaternary ammonium or phenolic products. Heat, sunlight, ultraviolet light, E-Beam, and Gamma Rays can also destroy the virus.  Health care workers who clean contaminated surfaces should wear personal protective equipment such as gloves, gowns, eye protection, and a face mask. 

The prevention of Ebola in Africa presents many challenges. Because the identity and location of the natural reservoir of Ebola virus are unknown, there are few primary prevention measures. When cases of the disease appear, social and economic conditions frequently favor the spread of an epidemic within healthcare facilities.

Health-care providers must have training to recognize Ebola and the capability to perform diagnostic tests. They must also be ready to employ practical viral hemorrhagic fever isolation precautions, or barrier nursing techniques. These techniques include the wearing of protective clothing, such as masks, gloves, gowns, and goggles; the use of infection-control measures, including complete equipment sterilization; and the isolation of Ebola patients from contact with unprotected persons. The purpose of these techniques is to avoid any person’s contact with the blood or secretions of any patient. If a patient with Ebola dies, it is equally important that direct contact with the body of the deceased patient be prevented. 

There are two treatment options that are approved by the FDA to treat Ebola caused by the Zaire ebolavirus strain. The first treatment, Inmazeb,  was approved in October 2020, and is a combination of three monoclonal antibodies (atoltivimab, maftivimab, and odesivimab-ebgn). This product targets the glycoprotein that is present on the surface of the Ebola virus and blocks it from attaching and entering the cell. The second treatment, Ebanga,  is a human monoclonal antibody that received FDA approval in December 2020. This product blocks the Ebola virus from binding to the cell receptor and prevents it from entering the cell and causing infection.

On December 19, 2019, the FDA approved ERVEBO, a genetically modified live Ebola virus vaccine for use in persons 18 years of age and older. This vaccine is manufactured by Merck and targets the Zaire ebolavirus strain.  The CDC’s Advisory Committee on Immunization Practices (ACIP) recommends this vaccine for persons responding to an outbreak of Ebola, healthcare workers treating patients at federally-designated Ebola Treatment Center in the U.S., and for laboratory personnel employed at biosafety-level 4 facilities in the United States. 

What is Ebola vaccine?

On December 19, 2019, the FDA approved ERVEBO (rVSV-ZEBOV), a genetically modified live Ebola virus vaccine for use in persons 18 years of age and older. This vaccine is manufactured by Merck and targets the Zaire ebolavirus strain.  ERVEBO is a live, genetically modified Ebola virus vaccine and uses an attenuated vesicular stomatitis virus, a pathogen that infects livestock (cattle, horses, deer, pigs) with one of its genes replaced by an Ebolavirus gene.    The virus used in the vaccine is grown in Vero cell cultures and is harvested from the cell culture medium, purified, formulated with stabilizer solution, transferred into vials and stored frozen. When thawed for use, ERVEBO is a colorless to slightly brownish-yellow liquid that has no visible particulates.

Each 1 mL dose of ERVEBO contains 72 million plaque-forming units (pfu) of vaccine virus in a stabilizer solution containing 2.5 mg/mL rice-derived recombinant human serum albumin and 10 mM Tromethamine (Tris). Each dose might also contain residual amounts of host cell DNA (≤10 ng), benzonase (≤15 ng) and trace amounts of rice protein. 

ERVEBO vaccine must be stored in the original container to protect the vials from light. Storage  temperatures of -80°C and -60°C (-112°F to -76°F) must be maintained and the product must be thawed at room temperature. Once thawed, it can be stored in a refrigerator between 2°C and 8°C (35.6°F to 46.4°F) for up to two weeks and at room temperature (up to 25°C; 77°F) for no more than four hours. Thawed vaccine product cannot be re-frozen. The vaccine must remain protected from light. 

The CDC’s Advisory Committee on Immunization Practices (ACIP) recommends this vaccine for adults 18 years and older responding to an outbreak of Ebola virus disease, healthcare workers treating patients at federally-designated Ebola Treatment Center in the U.S., and for laboratory personnel employed at biosafety-level 4 facilities in the United States.  It is also recommended for healthcare providers at specialized pathogen treatment centers and for support staff and laboratory workers at Laboratory Response Network facilities. 

What is the history of Ebola vaccine?

The first Ebola virus vaccine, ERVEBO, was initially developed in Canada by scientists from the Public Health Agency of Canada’s National Microbiology Laboratory. The vaccine was made by modifying an attenuated strain of a vesicular stomatitis virus (VSV) to permit the expression of an Ebola protein.  The license for the vaccine was first held by NewLink Genetics, a U.S. company that was eventually absorbed into Lumos Pharma.   

When an Ebola outbreak emerged in Western Africa in early 2014, Canada offered its experimental vaccine to the World Health Organization (WHO). The organization, however, declined this vaccine, as well as one that was under development by GlaxoSmithKline (GSK). A few days after the WHO declared the Ebola outbreak a global health emergency, the Canadian government announced that it would be donating the experimental vaccine to the agency. 

The vaccine, however, had never been tested in clinical trials, and while drug companies have an extensive history of using experimental products on persons living in developing countries, WHO decided that clinical trials would be necessary. NewLink Genetics had never conducted large-scale clinical trials and as a result, WHO and other world leaders pushed for the company to partner with or sell the vaccine rights to a larger pharmaceutical company. In late 2014, Merck pharmaceuticals bought the Ebola vaccine rights for $50 million. 

The experimental vaccine, which targeted the Zaire ebolavirus, was evaluated in Guinea during the 2014-2016 Ebola outbreak in West Africa. The Phase 3 trial was an open-label, cluster-randomized, controlled ring vaccination trial where clusters of contacts of persons who were confirmed to have Ebola virus and contacts of those contacts were offered immediate vaccination or delayed vaccination (a vaccine after a 21 days).The main outcome of interest was the number of laboratory-confirmed Ebola virus cases occurring at 10 or more days following randomization. This 10-day period was chosen to account for the Ebola virus incubation period and the unknown time frame from vaccination to the development of vaccine-acquired immunity. 

The analysis of the randomized clusters in the initial study found that among the 2,108 individuals who immediately received the vaccine, no cases of Ebola virus disease occurred 10 or more days after randomization. However, 10 of 1,429 participants in the delayed group developed Ebola virus disease after randomization. The vaccine was reported to have an efficacy of 100 percent in persons in the immediate vaccination group. 

These findings, however, were questioned by independent researchers who stated the following: 

“This perfect vaccine efficacy could be true if the two groups had been comparable in all variables but the vaccination. However, the protocol of this cluster-randomised trial reveals a bias with respect to the intervention. After randomisation, people in both types of clusters (immediate and delayed vaccination) were visited by a medical study team and a surveillance team, but the medical study team did not stay in the communities of the delayed vaccination (control) clusters. People in the control clusters were only visited by the medical study team on day 0 to identify controls and obtain informed consent and then on day 21 to vaccinate the controls. By contrast, for the immediately vaccinated clusters, the medical study teams stayed in the communities to follow up the vaccinated participants with active and passive detection of side-effects. The presence or absence of a medical team attending study participants in an African community will have an effect on outcomes. Continuous interaction with the doctors and nurses of the study team for 3 weeks would have affected the knowledge and behaviour (eg, awareness of disease symptoms, keeping distance, general rules of hygiene) of the participants, which in turn would have affected disease transmission. Such changes in knowledge and behaviour are especially important when the basic reproduction number of transmission is very low, as is the case with the Ebola virus. Thus, zero cases in the immediately vaccinated clusters of this unblinded study might have been the result of other factors than the vaccine, and vaccine efficacy might have been lower than 100%. All possible cases of Ebola virus disease might have been averted by behavioural change; in such case, the vaccine efficacy would have been 0%.”

The researchers also warned that inaccurate vaccine efficacy data might have serious and potentially fatal consequences if vaccinated individuals did not follow stringent infection control measures because they assumed complete protection from vaccination. 

Adverse events reported during clinical trials of ERVEBO included: injection site pain, swelling, and redness; headache; fever; nausea; fatigue; muscle pain; joint pain, swelling, stiffness, warmth, and redness; abnormal sweating; rash; mouth ulcers; vesicular lesions; arthralgia; arthritis; anaphylaxis; cerebrovascular accident (a type of stroke); hemorrhagic stroke; subarachnoid hemorrhage; pulmonary embolism; and death. 

Arthralgia and severe arthralgia were reported at higher rates in persons vaccinated with ERVEBO in comparison to placebo recipients.  In some cases, vaccinated individuals experienced persistent and recurrent joint pain. In studies, all joint types were noted to be affected. Persons with a past history of arthritis and females were found to be at a higher risk of arthritis post-vaccination. 

The vaccine received full approval for use by the European Commission in November 2019 after the European Medicines Agency (EMA) recommended its use.  One month later, on December 19, 2021, Merck’s ERVEBO Ebola virus vaccine received FDA approval for use in persons 18 years of age and older. This vaccine targets Ebola virus disease (EVD), caused by Zaire ebolavirus, and is administered as a single dose. 

On February 26, 2020, the CDC’s Advisory Committee on Immunization Practices (ACIP) voted to recommend pre-exposure vaccination of ERVEBO in adults 18 years of age and older who are considered at highest risk of developing Ebola virus disease. These populations include individuals responding to an outbreak of Ebola virus disease, health care personnel working at a federal facility designed to treat persons with Ebola virus diseases, and persons working at a biosafety level 4 facility where Ebola virus is present.  ACIP expanded its recommendation for use of the vaccine in 2021 to include healthcare workers providing care at specialized pathogen treatment centers and laboratory and support staff working at Laboratory Response Network facilities. 

How effective is Ebola vaccine?

According to the ERVEBO package insert,  efficacy of the vaccine was studied in the Ring Vaccination Study (Study 3). This study was an open-label, randomized cluster study that took place in the Republic of Guinea during the 2014 outbreak.

Each cluster was comprised of contacts and contacts of contacts of persons with laboratory-confirmed Ebola virus disease (EVD). Clusters were randomized to be given either an “immediate” vaccination or a 21-day “delayed” vaccination.

3,537 subjects ≥18 years of age were considered contacts and contacts of contacts of an index case with laboratory-confirmed EVD in the primary efficacy analysis. Of these, 2,108 were involved in 51 immediate vaccination clusters, and 1,429 were involved in 46 delayed vaccination clusters.

The median age of individuals involved in the primary efficacy analysis was 40 years. Most of the participants were male, with 70.4 percent involved in the randomized immediate cluster and 70.3 percent in the delayed clusters.

In the primary efficacy analysis, the number of laboratory-confirmed EVD cases in persons vaccinated in the immediate vaccination clusters was compared to the number of cases in persons in the delayed vaccination clusters. Cases of EVD occurring between Day 10 and Day 31 post-randomization of the cluster were included in the analysis. No cases of confirmed EVD were noted in the immediate vaccination clusters and the vaccine efficacy was determined to be 100 percent (95% CI: 63.5% to 100%). Ten confirmed cases of EVD were noted among four delayed vaccination clusters and these occurred between Day 10 and Day 31 post-randomization. 

These findings, however, have been questioned by independent researchers who stated the following: 

“This perfect vaccine efficacy could be true if the two groups had been comparable in all variables but the vaccination. However, the protocol of this cluster-randomised trial reveals a bias with respect to the intervention. After randomisation, people in both types of clusters (immediate and delayed vaccination) were visited by a medical study team and a surveillance team, but the medical study team did not stay in the communities of the delayed vaccination (control) clusters. People in the control clusters were only visited by the medical study team on day 0 to identify controls and obtain informed consent and then on day 21 to vaccinate the controls. By contrast, for the immediately vaccinated clusters, the medical study teams stayed in the communities to follow up the vaccinated participants with active and passive detection of side-effects. The presence or absence of a medical team attending study participants in an African community will have an effect on outcomes. Continuous interaction with the doctors and nurses of the study team for 3 weeks would have affected the knowledge and behaviour (eg, awareness of disease symptoms, keeping distance, general rules of hygiene) of the participants, which in turn would have affected disease transmission. Such changes in knowledge and behaviour are especially important when the basic reproduction number of transmission is very low, as is the case with the Ebola virus. Thus, zero cases in the immediately vaccinated clusters of this unblinded study might have been the result of other factors than the vaccine, and vaccine efficacy might have been lower than 100%. All possible cases of Ebola virus disease might have been averted by behavioural change; in such case, the vaccine efficacy would have been 0%.”

The researchers also warned that inaccurate vaccine efficacy data might have serious and potentially fatal consequences if vaccinated individuals did not follow stringent infection control measures because they assumed complete protection from vaccination. 

A March 2020 study on 257 patients admitted to the Ebola Treatment Units (ETU) in the Eastern Democratic Republic of the Congo (DRC) reported that vaccinated individuals had a higher survival rate. In this study, 44 of the 257 patients had been vaccinated but were admitted for treatment of Ebola. Study authors noted that vaccinated individuals had lower viral levels and were less likely to suffer from kidney injury, but also reported that 23 percent (10/44) died of the disease. 

The measure of immune response that is indicative of protection against EVD is unknown. Additionally, persons who receive ERVEBO could have an immune response that might prevent laboratory tests from differentiating between wild-type and vaccine-strain Ebola infection. The ERVEBO package insert reports that “the vaccine virus RNA has been detected by RT-PCR in blood, saliva, urine, and fluid from skin vesicles of vaccinated adults” and that “transmission of vaccine virus is a theoretical possibility.” This means that the vaccine has the potential to infect others with vaccine-strain Ebolavirus due to virus shedding. 

Can Ebola vaccine cause injury & death?

Adverse events reported during clinical trials of ERVEBO included: injection site pain, swelling, and redness; headache; fever; nausea; fatigue; muscle pain; joint pain, swelling, stiffness, warmth, and redness; abnormal sweating; rash; mouth ulcers; vesicular lesions; arthralgia; arthritis; anaphylaxis; cerebrovascular accident; hemorrhagic stroke; subarachnoid hemorrhage; pulmonary embolism; and death. 

White blood cell counts were evaluated in nearly 700 individuals who received ERVEBO. Decreases in neutrophils were noted in at least 43 percent of vaccine recipients and 85 percent experienced a decrease in lymphocytes.  Neutrophils, a type of white blood cell, are vital to the immune system as they attack and destroy bacteria that invade the body. Low neutrophil counts can put an individual at a higher risk of serious infection.  Leukocytes, another type of white blood cell, are also critical to the immune system and protect the body against infection. 

Arthralgia (joint pain) and severe arthralgia occurring between Day 0 and Day 42 were reported at higher rates in persons vaccinated with ERVEBO in comparison to placebo recipients.

There was a higher rate of arthritis occurring between Day 5 and 56 among ERVEBO vaccine recipients.  In some cases, vaccinated individuals experienced persistent and recurrent joint pain. In studies, all joint types were noted to be affected. Persons with a past history of arthritis and females were found to be at a higher risk of arthritis post-vaccination. 

Women who were inadvertently vaccinated or who became pregnant within 60 days of ERVEBO vaccination were also found to be at a higher risk of miscarriage. Eighty-four women were unintentionally vaccinated in early pregnancy or within two months of vaccination or enrollment in the clinical trial. Forty-five percent (14 of 31) of pregnant women who were immediately vaccinated experienced a miscarriage in comparison to 33 percent (11 of 33) of unvaccinated women. 

Using the MedAlerts search engine, from FDA approval in December 2019 through March 29, 2024, there have been 52 reports of Ebola vaccine reactions, hospitalizations, injuries, and deaths following Ebola vaccination made to the federal Vaccine Adverse Events Reporting System (VAERS), including 3 hospitalizations, 3 related disabilities and 1 related deaths.

Who is at highest risk for complications from Ebola vaccine?

In clinical trials of ERVEBO Ebola Virus Vaccine, arthritis was found to occur in up to 24 percent of vaccine trial participants. Arthritis events included osteoarthritis, monoarthritis, polyarthritis, joint effusion, and joint swelling. One study conducted in Switzerland reported that 24 percent of participants developed arthritic conditions, with some people having symptoms that persisted long-term or recurred. 

Persons with a past history of arthritis and females were found to be at a higher risk of arthritis post-vaccination. 

Women who are inadvertently vaccinated during pregnancy or who become pregnant within two months of vaccination may be at higher risk of miscarriage. Eighty-four women were unintentionally vaccinated in early pregnancy or within two months of vaccination or enrollment in the clinical trial. Forty-five percent (14 of 31) of pregnant women who were immediately vaccinated experienced a miscarriage in comparison to 33 percent (11 of 33) of unvaccinated women. 

Who should not get Ebola vaccine?

Persons who have previously experienced a severe allergic reaction to any ingredient contained within the ERVEBO vaccine should not be vaccinated. ERVEBO contains recombinant human serum albumin derived from rice. Individuals who have previously experienced an allergic reaction to rice protein should not be vaccinated. 

Public health officials report that there is insufficient human data from clinical trials to determine the risk of ERVEBO vaccination during pregnancy. Vaccination of pregnant women should take into consideration the risk of disease and the potential for adverse events associated with vaccination. Additionally, data is absent on the effect of ERVEBO vaccination on human milk, its presence in human milk, and the impact on the breastfed baby. Breastfeeding women who are contemplating ERVEBO vaccination should consider disease risk as well as the potential for vaccine-related adverse events. 

Data is also insufficient to assess the safety and efficacy of ERVEBO vaccination on persons with immunodeficient conditions. Limited information is available on the use of the vaccine in persons with stable HIV disease. 

ERVEBO is a replication-competent, live attenuated virus vaccine. Vaccinated individuals may be capable of transmitting the vaccine virus on to close contacts. Vaccine virus RNA has been detected in the urine of vaccinated individuals as long as seven days post-vaccination, and in the saliva and blood for as long as 2 weeks. Additionally, the vaccine virus has been detected in skin vesicles and synovial fluid for as long as 20 days after vaccination. To prevent the risk of vaccine-virus transmission, vaccine recipients should: 

• Avoid sharing personal items such as toothbrushes, drinking from the same cup, sharing razors, or open mouth kissing for at least two weeks after vaccination. If an individual develops oral lesions post-vaccination, these activities should be avoided until healed
• Refrain from donating blood for at least 6 weeks post-vaccination
• Use an effective prophylaxis during sexual interactions for at least 2 months post-vaccination
• Avoid any activities that expose a high-risk person to blood and body fluids for at least 6 weeks. High-risk persons include children under 12 months of age, pregnant and breastfeeding women, and immunocompromised individuals.
• Avoid exposing livestock to blood and body fluids
• Cover any vesicular or maculopapular rash with a bandage until healed. Any contaminated bandages should be placed in a sealed plastic bag prior to disposal and hands should be washed with soap and water.

What questions should I ask my doctor about Ebola vaccine?

NVIC If You Vaccinate, Ask 8! downloadable brochure suggests asking eight questions before you make a vaccination decision for yourself, or for your child. If you review these questions before your appointment, you will be better prepared to ask your doctor questions. 

To be more fully informed about the vaccine, it is important to read the vaccine manufacturer’s product insert if you are considering Ebola vaccination. Federal law requires drug companies marketing vaccines to include certain kinds of vaccine benefit, risk and use information in product information inserts. The Ebola vaccine package insert is located on the Food and Drug Administration’s website and is also available under NVIC’s Quick Facts.

NVIC provides the public with referenced information on both the disease and vaccine to empower informed decision-making and encourages consumers to further explore these references as vaccine decisions are made.

Other questions that may be useful to discuss with your doctor before getting the Ebola vaccine are: 

• If other vaccines in addition to Ebola vaccine are scheduled for me at this office visit, what policy is in place for me to modify the schedule so fewer vaccines are given at once?
• What should I do if I become ill after vaccination?
• What other kinds of reaction symptoms should I call to report after Ebola vaccination?
• If the Ebola vaccine doesn’t protect me, do I have any other options for preventing Ebola virus infection?

In alignment with the informed consent ethic, which has guided the ethical practice of modern medicine, vaccine providers should answer your questions, and/or provide you with resources to learn more. The informed consent ethic, which is recognized globally as a human right, also states that individuals should be able to delay or refuse treatments and interventions without coercion or punishment. 

Under federal law, vaccine providers are required to report vaccine adverse events to the federal Vaccine Adverse Event Reporting System (VAERS) that is co-administered by the CDC and FDA.  You can learn more about reporting vaccine reactions on NVIC’s reaction reporting webpage and can also directly report vaccine reactions to VAERS.

Vaccine Injury Compensation

In the U.S., vaccine manufacturers are shielded from liability under the 2005 Public Readiness and Emergency Preparedness (PREP) Act if a vaccine or drug developed in response to a health emergency like a pandemic causes the death or permanent injury of an individual who receives it during pre-licensure clinical trials or after it is released for public use.    The PREP Act was part of a series of “Bioshield” laws created in response to national security fears after 9/11 and subsequent reported weaponized microbe threats, which prompted Congress to encourage pharmaceutical companies to develop anti-bioterrorism vaccines by, in part, eliminating liability for injuries and deaths caused by those vaccines. 

Individuals who die or suffer serious harm due to the administration of covered countermeasures, such as vaccines, may be eligible to receive compensation through the Countermeasures Injury Compensation Program (CICP),  whether the harm was a result of willful misconduct on the part of the vaccine manufacturer or person administering the vaccine.

HHS has interpreted state and federal law to include tort and contract law, as well as claims for loss relating to compliance with local, state, or federal laws, regulations or other legal requirements. The definition of “loss” under the Act is broad, encompassing both physical and emotional injuries. Although the PREP Act does provide immunity to the pharmaceutical industry from Ebola vaccine injury lawsuits, vaccine manufacturers are not immune from injunctive relief or enforcement actions by the U.S. Food and Drug Administration (FDA) or other federal agencies. 

The CICP is administered by employees in HHS’s Health Resources and Services Administration. HRSA is the same agency responsible for administering the federal vaccine injury compensation program (VICP) created by Congress in 1986 under the National Childhood Vaccine Injury Act, which partially shielded vaccine manufacturers from liability for injuries and deaths caused by FDA licensed vaccines that are recommended by the CDC for children and mandated by states for school entry.  The 1986 Act was later amended to eliminate civil liability from doctors and other vaccine administrators and, in 2011, the U.S. Supreme Court eliminated remaining liability from vaccine manufacturers for defectively designed vaccines. 

HHS regulations govern CICP’s procedures and eligibility determinations. In general, eligible individuals (or their survivors) who suffer death or serious physical injury directly caused by the administration of a covered countermeasure may receive reimbursement for reasonable medical expenses, loss of employment income and survivor benefits in the case of death. Serious physical injuries under CICP are generally limited to those that warrant hospitalization or result in a significant loss of function or disability. Congress funds CICP awards through emergency appropriations to the Covered Countermeasure Process Fund. 

The CICP and the National Vaccine Injury Compensation Program (VICP) are separate programs managed by HRSA. CICP applies to countermeasures (vaccines and drugs) covered by a PREP Act declaration of a public health emergency, such as those issued for the Ebola virus outbreak in 2016,  while the VICP applies to vaccines recommended by the CDC for children and, as of 2016 under the 21^st Century Cures Act, vaccines recommended for pregnant women. 

Remember, if you choose to vaccinate, always keep a written record of exactly which shots/vaccines you or your child have received, including the manufacturer’s name and vaccine lot number. Write down and describe in detail any serious health problems that develop after vaccination and keep vaccination records in a file you can access easily.  

It also is important to be able to recognize a vaccine reaction and seek immediate medical attention if the reaction appears serious, as well as know how to make a vaccine reaction report to federal health officials at the Vaccine Adverse Reporting System (VAERS). NVIC’s Report Vaccine Reactions—It’s the Law webpage can help you file a vaccine reaction report yourself to VAERS if your doctor fails or refuses to make a report.

NVIC Press Releases, Statements & Commentaries Related to Ebola Virus

NVIC Articles

• Will There Be An Ebola Outbreak in America? – Oct. 15, 2014.

The Vaccine Reaction

• TVR Staff Merck Plans to Up Production of Experimental Ebola Vaccine The Vaccine Reaction July 28, 2019.
• Cáceres M Merck’s Ebola Vaccine, A Christmas Gift for the World: Really? The Vaccine Reaction Dec. 27, 2016.

Ebola Disease and Vaccine Quick Facts

Quick Facts

Ebola (Ebola Hemorrhagic Fever)

• Ebola is a serious contagious disease with a high mortality rate. The incubation period from initial exposure to onset of acute disease symptoms is between 2 and 21 days with the average being 8 to 10 days. Symptoms start with a fever, headache, muscle and stomach pain, diarrhea, vomiting, and skin bruising and may also include a skin rash, red eyes, and hiccups.  Additional symptoms may include shortness of breath, chest pain, confusion, seizures, and bleeding. White blood cell and platelet counts decrease and both internal and external bleeding can occur. Fatal cases usually present with more severe symptoms early in the course of the illness, and death generally occurs from sepsis or multiorgan failure between day 6 and 16. 

• The Ebola virus is transmitted through direct contact with infected blood or body fluids, or by coming into contact with objects infected by the virus. It can also be spread through exposure to infected primates (apes, monkey, etc.) or fruit bats. A person with Ebola virus is only contagious to others after they begin to show signs of illness. 

• Treatment of Ebola virus disease includes intravenous fluid administration, oxygen supplementation, blood pressure monitoring and stabilization, and treatment of any secondary infections. There are two treatments currently approved for use by the U.S. Food and Drug Administration (FDA) to treat Ebola virus disease caused by species Zaire ebolavirus in children and adults.  The first approved treatment, Inmazeb,  is a combination of three monoclonal antibodies and the second treatment, Ebanga,  is a human monoclonal antibody.

• Persons who survive Ebola virus disease develop long-term immunity; however, health problems frequently persist upon recovery. Common symptoms include fatigue, headaches, weight gain, vision disturbances, joint and muscle pain, loss of appetite, and stomach pain. Additional long-term health issues can also include dry mouth, neck swelling, tightness of the chest, hearing problems, memory problems, tingling and pain in the hands and feet, changes in menstruation, impotence, inflammation of the testicles, decreased sex drive, sleep disturbances, inflammation of the tissues surrounding the heart, anxiety, depression, and post-traumatic stress disorder. 

• Ebola virus disease was initially discovered in 1976 after two separate outbreaks of hemorrhagic fever occurred in different areas of Central Africa. The first occurred in the Democratic Republic of Congo, near the Ebola River, and the second occurred approximately 500 miles away, in South Sudan. 

 Ebola Vaccines

• On December 19, 2019, the FDA approved Merck’s ERVEBO Ebola vaccine, a genetically modified live Ebola virus vaccine for use in persons 18 years of age and older.  The vaccine targets the species Zaire ebolavirus. The CDC’s Advisory Committee on Immunization Practices (ACIP) recommends that ERVEBO be given to all persons responding to an outbreak of Ebola virus disease, healthcare workers treating patients at federally-designated Ebola treatment centers in the U.S., biosafety-level 4 laboratory personnel,  healthcare personnel at specialized pathogen care centers, and to support and laboratory staff at Laboratory Response Network facilities. 

• The ERVEBO package insert reports that the vaccine has the potential to infect others with vaccine-strain Ebolavirus due to virus shedding. 

• Adverse events reported during clinical trials included: injection site pain, swelling, and redness; headache; fever; nausea; fatigue; muscle pain;  joint pain, swelling, stiffness, warmth, and redness; abnormal sweating; rash; vesicular lesions; arthralgia; arthritis; and anaphylaxis. 

• The vaccine package insert also noted that white blood cell counts were evaluated in nearly 700 individuals who received ERVEBO. Decreases in neutrophils were noted in at least 43 percent of vaccine recipients, and 85 percent experienced a decrease in lymphocytes.  Neutrophils, a type of white blood cell, are vital to the immune system as they attack and destroy bacteria that invade the body. Low neutrophil counts can put an individual at a higher risk of serious infection.  Leukocytes, another type of white blood cell, are also critical to the immune system and protect the body against infection.  Additionally, persons who receive ERVEBO could have an immune response that might prevent laboratory tests from differentiating between wild-type and vaccine-strain Ebola infection. 

• Using the MedAlerts search engine, from FDA approval in December 2019 through March 29, 2024, there have been 52 reports of Ebola vaccine reactions, hospitalizations, injuries, and deaths following Ebola vaccination made to the federal Vaccine Adverse Events Reporting System (VAERS), including 3 hospitalizations, 3 related disabilities, and 1 related death.

 

IMPORTANT NOTE: NVIC encourages you to become fully informed about Ebola and the Ebola vaccine by reading all sections in the Table of Contents, which contain many links and resources such as the manufacturer product information inserts, and to speak with one or more trusted health care professionals before making a vaccination decision for yourself or your child. This information is for educational purposes only and is not intended as medical advice.

 

Centers for Disease Control (CDC)

• CDC on the Ebola Virus
• CDC Ebola Outbreaks
• Ebola Virus Disease (EVD) Information for Clinicians in U.S. Healthcare Settings

 

Food and Drug Administration (FDA)

• ERVEBO (Ebola Zaire Vaccine, Live) – Merck Sharp & Dohme Corp. - Package Insert and Licensing Information

• Ebola Preparedness and Response Updates from FDA

 

National Institutes of Health (NIH) and Affiliates

• Ebola Vaccines
• Ebola & Marburg

 

World Health Organization (WHO)

• Ebola Virus Disease - WHO Fact Sheet, Feb 23, 2021

 

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