Key takeaways:

• The trial could roll out in about 6 weeks in the DRC’s Ituri province.
• An expert called the trial “an important development” but said a Bundibugyo-specific vaccine is what is needed most.

Plans are underway to launch a phase 3 trial of an existing Ebola vaccine to fight the ongoing deadly outbreak in the Democratic Republic of the Congo, WHO told Healio.

The trial could begin by mid-September, a much faster timeline than the 5 to 12 months typically needed for clinical trials being conducted outside an outbreak zone, WHO noted.

WHO plans to launch a phase 3 trial of an existing Ebola vaccine in the DRC outbreak.

Currently, no approved vaccine exists for the rare species of Ebola, Bundibugyo ebolavirus, that is causing the outbreak, which has killed more than 2,000 people in the DRC as of Aug. 9, according to the CDC.

Instead, the phase 3 trial will use a vaccine, Ervebo (Merck), that gained approval in 2019 for a different Ebola species, Orthoebolavirus zairense. The vaccine was tested in a ring-vaccination trial during the West African epidemic — the deadliest Ebola outbreak on record — and has been deployed successfully numerous times to stop outbreaks of Orthoebolavirus zairense in the DRC.

Researchers recently tested Ervebo in a laboratory setting using serum samples from a prior study and found it may offer cross-protection against the Bundibugyo virus, according to results published in The New England Journal of Medicine.

WHO said it took the lead in designing the upcoming trial, which will be “implemented by a consortium” that includes the DRC’s National Institute of Biomedical Research, the Coalition for Epidemic Preparedness Innovations, the Institute of Tropical Medicine in Belgium, Doctors Without Borders and the Africa CDC.

At a meeting on July 31, WHO’s vaccine advisory board recommended prioritizing Ervebo for inclusion in a phase 3 trial in the DRC, according to a summary of the discussions published last week.

WHO said the trial could start 6 weeks from the time of the board’s recommendation, but the agency noted that a launch date “will depend on when DRC authorities approve the protocol, when vaccine can be shipped to Ituri province and teams trained on the trial procedures.”

Jennifer B. Nuzzo, DrPH, a professor of epidemiology and director of the Pandemic Center at Brown University School of Public Health, told Healio that the trial is “an important development” and “may be an expedient approach to lessening the severity of illness.”

“There are scientific questions that need to be answered,” Nuzzo said. “But ultimately, the biggest challenges are likely to be operational. That includes making sure people at-risk, like healthcare workers, can get the vaccine in an insecure setting.”

She said a Bundibugyo-specific vaccine is what is needed most. Both the Oxford Vaccine Group and Moderna recently announced new experimental human trials of vaccines targeting the Bundibugyo species.

“We need to think long term,” Nuzzo said. “This won't be the last outbreak — the DRC alone has been home to 17 Ebola outbreaks. We need to think about establishing population protection against future outbreaks, not just ending this one.”

For more information:

Jennifer Nuzzo, DrPH, can be reached at infectiousdisease@healio.com.