MARY LOUISE KELLY, HOST:
Outbreaks of the deadly Ebola virus flare up in parts of Africa almost every year. The virus kills about half the people it infects. But a new study shows that a vaccine already in use is offering even more protection than previously thought. Here's science reporter Ari Daniel.
ARI DANIEL, BYLINE: Ebola is no joke. Oyewale Tomori is a virologist, now retired from Redeemer's University in Nigeria. During his career, he investigated outbreaks in the Democratic Republic of Congo and Nigeria. Tomori says people with Ebola have a ghostlike appearance.
OYEWALE TOMORI: Bleeding from the orifices. They are weak. They can't move. It's a very devastating experience for those who have it.
DANIEL: And in about half the cases, it's lethal. For years, there wasn't much that could be done. But with time, researchers developed ways to fight back, including better treatments and two vaccines, one of which is a single-dose vaccine that expresses one of Ebola's main proteins.
REBECCA COULBORN: So later, if the person is exposed to Ebola, their immune system will recognize the viral protein.
DANIEL: Rebecca Coulborn is an epidemiologist with Epicentre, the medical research arm of Doctors Without Borders.
COULBORN: And this recognition allows the immune system to be prepared to attack the virus and protect the person from Ebola virus disease.
DANIEL: Coulborn says the vaccine is not administered as part of a mass immunization campaign. It is used strategically in areas where Ebola flares up.
COULBORN: This has been traditionally administered as targeting people who are contacts of an Ebola case, contacts of contacts and health care workers.
DANIEL: A method called ring vaccination. Now, the vaccine has been shown to be highly effective at reducing the risk of infection. But the researchers wanted to know, what about those who are vaccinated during an epidemic but then go on to contract Ebola anyway? Could being vaccinated protect them from dying? They focus their efforts on the second-largest Ebola outbreak ever recorded in the Democratic Republic of Congo between 2018 and 2020. Despite the outbreak blazing in the midst of a brutal conflict zone, health officials were able to keep meticulous records.
COULBORN: Across the entire Ebola epidemic, they standardized, harmonized and compiled list of all admissions to the Ebola health facilities.
DANIEL: This list included nearly 2,300 patients. It told Coulborn whether or not each person had been vaccinated before they got sick and when they'd received the vaccine. She then compared the two groups. The result was striking. For those who'd been vaccinated, their risk of dying fell by more than half.
COULBORN: Patients who had not been vaccinated had a mortality of 56%, while patients who received the vaccine had a mortality of 25%. And that's huge.
DANIEL: And this was true no matter when someone got vaccinated before the onset of symptoms, whether just a couple days or more than three weeks.
COULBORN: So while getting vaccinated as early as possible is the most beneficial, we now know that vaccination is better late than never.
DANIEL: The findings are published in the journal The Lancet Infectious Diseases. Here's Oyewale Tomori again, who wasn't involved in the study.
TOMORI: So this is really exciting news for those of us who are involved in Ebola studies.
DANIEL: Tomori says it points to how critical vaccination campaigns are not just before an outbreak but during one, too. For Rebecca Coulborn, the results come as welcome news in the battle against this terrible disease.
COULBORN: Working in this field has become, I would say, much more hopeful.
DANIEL: Now that there's a vaccine that offers a meaningful chance of surviving Ebola. For NPR News, I'm Ari Daniel.
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