Ebola vaccine Ervebo trial urged as DRC cases top 4,000

WHO vaccine experts recommended a full-scale human trial of Ervebo, the only licensed Ebola vaccine, to test whether it can protect people against the Bundibugyo strain spreading in the Democratic Republic of Congo, where confirmed cases have reached 4,053, including 1,850 deaths.

The World Health Organization said its technical advisory group recommended that Ervebo be prioritised for a randomised clinical trial during the outbreak. A WHO spokesman said the proposed study would be a ring trial in the DRC, involving contacts around known cases.

Ervebo has been proven safe and effective against the more common Zaire strain of Ebola. WHO experts said early data, including animal studies, suggest it may offer some protection against Bundibugyo. One study found that three of four non-human primates vaccinated with Ervebo survived Bundibugyo exposure, compared with one of four control animals. An unpublished ferret study found that a research-grade version of Ervebo provided 100-percent protection, while all control animals died within 10 days.

The experts said there were no safety concerns about using Ervebo in a clinical research study vaccinating case contacts, noting that it is already licensed and has been given to hundreds of thousands of people in Africa. They also said expectations should be managed because protection against symptomatic disease and transmission may not be high, although protection against death may be achieved.

A vaccine designed specifically for Bundibugyo remains the preferred option for the current outbreak, the experts said. Two potential Bundibugyo vaccines are in early human trials, and a third is being developed to reach that stage.

The Gavi vaccine alliance said it maintains a stockpile of 500,000 Ervebo doses and that doses from the stockpile would be made available for the trials, with some already in the DRC. Gavi said around 55,000 frontline workers in Ituri and North Kivu have received Ervebo through previous preventive vaccination campaigns.

Around 87 percent of cases in the DRC outbreak are in the northeastern province of Ituri, with 11 percent in neighbouring North Kivu. WHO director-general Tedros Adhanom Ghebreyesus warned that the virus was spreading faster than response efforts could catch up.