Who Should Receive the New Ebola Vaccine?

Sandra Adamson Fryhofer, MD


September 22, 2020

This transcript has been edited for clarity.

Hello. I'm Dr Sandra Fryhofer.

COVID-19 has been a sobering reminder of what can happen when a new virus hits and there's no treatment, no cure, and no vaccine. But for an even deadlier virus, Ebola, there is some good news.

On December 19, 2019, FDA approved a vaccine to prevent the deadliest strain, the Zaire Ebola virus. This is the strain linked to the majority of outbreaks since 1976, including the 2014 outbreak in West Africa and the 2020 outbreak in the Democratic Republic of the Congo (DRC).

Ebola is transmitted person-to-person by contact with infected tissue or body fluid of someone who's sick or has died from it. The virus can be found in all body fluids of those infected: blood, urine, feces, vomit, tears, and saliva. It can also be found in breast milk, amniotic fluid, vaginal secretions, semen, and even sweat. Exposure to contaminated surfaces, bedding, and clothing can also spread disease.

The incubation period is 2-21 days (most commonly, about 10 days). Ebola is highly transmissible but not contagious until symptoms start. The onset of illness can be sudden and severe. Symptoms include fever, headache, fatigue, muscle pain, joint pain, vomiting, diarrhea, abdominal pain, and rash. Some patients bleed both internally and externally.

Ebola in humans is deadly. Severe disease with death usually occurs 7-10 days after onset of symptoms. Untreated, the mortality rate is 70%-90%. Supportive care can improve survival to about 40%. Those who survive often suffer joint aches, muscle aches, abdominal pain, fatigue, and uveitis (that can lead to cataracts and blindness). Ebola virus can persist in testes, eyes, brain, and placental tissue. This persistence has been linked to additional disease transmission.

The new Ebola vaccine (brand name Ervebo) is a live attenuated recombinant vesicular stomatitis virus vaccine, called rVSV for short. The vaccine is made by removing a glycoprotein from a vesicular stomatitis virus and replacing it with a glycoprotein from Ebola virus. The vaccine cannot cause Ebola.

Vaccine-related serious adverse events reported so far are rare. The most common side effects include injection-site pain, swelling, erythema, fever, muscle aches, malaise, and headache. Arthralgia and arthritis have been reported after vaccination. The vaccine rVSV virus has been detected post-vaccination in blood, saliva, urine, and synovial fluid. The significance of this is unclear.

One dose given intramuscularly has vaccine efficacy of 100%.

The Ebola vaccine has to be stored frozen at -80˚ to -60˚ C. It can be stored at 2˚-8˚ C for up to 2 weeks, but once thawed, it cannot be refrozen. The vaccine seems to last up to 2 years.

The Ebola work group's evidence-based evaluation was presented to ACIP at its February 2020 meeting. Deliberations focused on pre-exposure vaccination for those at immediate occupational risk. Initially the workgroup submitted language recommending it only for nonpregnant individuals. After discussions focused on the deadly nature of this disease, it was decided to make the recommendation risk-based and more inclusive.

ACIP unanimously voted to recommend pre-exposure vaccination with Ebola vaccine for adults aged 18 and older at potential risk for exposure, including responders to an outbreak, healthcare personnel at federally designated Ebola treatment centers, and those working in biosafety level 4 facilities.

Currently there is no FDA-approved treatment for Ebola, but at least we now have a vaccine to prevent it. I'm Dr Sandra Fryhofer.

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