Ebola vaccine cuts mortality figures in half for people infected with the virus

The Ebola outbreak killed 55 people – Copyright AFP CARL DE SOUZA

New findings show vaccination reduces not only the risk of Ebola infection, but also the risk of death.

This is based on a new Doctors Without Borders/Médecins Sans Frontières (MSF) study published in The Lancet Infectious Diseases. This study shows, for the first time, that being vaccinated—even after being exposed to the Ebola virus—can cut mortality figures of those infected in half.

The observational study was conducted by MSF’s research arm, Epicentre and focused on the rVSVΔG-ZEBOV-GP vaccine. This drug product is produced by the pharmaceutical company Merck under the name Ervebo. The review was performed during the 2018-2020 Ebola epidemic in the Democratic Republic of Congo (DRC).

This study found that of the 2,279 confirmed Ebola patients admitted to Ebola health facilities between July 27, 2018 and April 27, 2020, the risk of dying was 56 percent among unvaccinated patients but fell to 25 percent for those who had received the vaccine.

This reduction in mortality applied to all patients, regardless of age or gender. MSF’s Epicentre conducted this study with the Institut National de Recherche Biomédicale (INRB) and DRC’s ministry of health.

Commenting on the research, Rebecca Coulborn, an epidemiologist with MSF’s Epicentre, states: “Vaccination after exposure to a person infected with Ebola virus disease—even when administered shortly before the onset of symptoms—still confers significant protection against death”.

rVSVΔG-ZEBOV-GP is effective against the especially deadly Zaire strain of Ebola. The drug is the only Ebola vaccine recommended for use during an epidemic like the one in DRC in 2018-2020.

Designed to be administered in a single dose, the medicine is recommended primarily for ring vaccination. Ring vaccination is a strategy that targets contacts and contacts of contacts of confirmed Ebola cases, as well as health care and frontline workers who are at high risk of exposure.

The goal is always to vaccinate people as early as possible during outbreaks; however, these new findings show that vaccinating someone who has already been exposed but is not yet symptomatic can also reduce the risk of death.

These new findings help make a case for the use of a combination of vaccination and treatment after someone is exposed to the virus. This will enable researchers to consider combining vaccination and treatment of patients who have been in direct contact with a person with confirmed Ebola virus disease in order to reduce the risk of illness and death.