A person’s chance of dying from Ebola increases substantially every day until he or she receives treatment, according to results from a landmark clinical trial conducted during a large epidemic in a violent region of the Democratic Republic of Congo.
The study, published Wednesday in the New England Journal of Medicine, confirmed that two experimental drugs outperformed two others in saving the lives of people stricken with the deadly viral disease in northeastern Congo.
The analysis also showed that patients’ odds of dying rose 11% for each day that they had symptoms before treatment began.
“This shows how acute Ebola virus disease can be,” said Sabue Mulangu, a co-lead author of the study and a researcher at the National Institute of Biomedical Research in Congo’s capital of Kinshasa.
The findings, based on an analysis of 673 patients, help explain why the world’s second-largest Ebola epidemic has proven so persistent and deadly, despite new drugs and a vaccine.
Of 3,298 cases of Ebola reported since August 2018, 2,197 died, yielding a 67% mortality rate, according to the World Health Organization.
Many people haven’t sought medical treatment or have sought it too late to be helped. Some have suspected that health-care workers are part of a plot to harm them.
Violence has also complicated medical care as well as the running of the clinical trial. Doctors and clinical-trial field teams have dodged attacks by armed groups, and two of the treatment centers they were working in were set on fire.
According to the new study, death rates were much lower for those patients who received the investigational therapies when they weren’t yet severely ill, when levels of the virus in their blood were low. “Viral load,” as the virus levels are called, tends to be lower early in the course of a disease.
“There’s a correlation,” said Richard Davey, another co-lead author and deputy clinical director at the U.S. National Institute of Allergy and Infectious Diseases.
People who were given a cocktail of three antibodies made by Regeneron Pharmaceuticals Inc., called REGN-EB3, had a 34% mortality rate overall. Patients with low viral loads, however, had an 11% death rate.
Of patients given a single-antibody drug called mAb114, developed by the NIAID, 35% died overall. Among those with low viral loads, 10% died.
A quarter of patients in the study said they had received an Ebola vaccine, which could have made their disease less severe. The role that vaccination played needs to be studied further, Dr. Davey said.
A vaccine by Merck & Co. has been given throughout the epidemic to people at risk of exposure to Ebola. The epidemic would have been larger without the vaccine, public health officials have said. Testing of a second vaccine from Johnson & Johnson recently got under way.
Regeneron and Ridgeback Biotherapeutics LP, a Miami biotech company that licensed the NIAID drug, have said they plan to seek approval from the U.S. Food and Drug Administration under a speedy review process for breakthrough drugs.
An editorial published along with the study in the New England Journal of Medicine said community education can help encourage patients to seek care when they first feel sick.
“But early care of patients also requires the availability of rapid diagnostics and ease of travel to treatment centers,” wrote Myron M. Levine of the University of Maryland School of Medicine in Baltimore, author of the editorial. “These issues must be addressed in future Ebola outbreaks.”
The number of new Ebola cases has slowed significantly in recent weeks, raising hopes that the epidemic could finally end soon, after more than a year. But new violence erupted recently in the city of Beni, where health workers are still caring for Ebola patients and trying to find others they may have infected. A field team for an extension phase of the drug trial is also working there.
“It’s hurting our operations,” Ibrahima Soce Fall, the WHO’s assistant director-general for emergency response, said in an interview. “We have been really, really struggling.”
The WHO evacuated 55 staff temporarily from Beni, Dr. Fall said, following violence by rebel forces, then attacks by angry residents on United Nations buildings. Dr. Fall added that 70 staff remain in Beni. The clinical trial field team is closely monitoring security reports, trial leaders said.
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