WHO urges Ervebo vaccine trial in DR Congo Ebola outbreak

(AFP) — WHO vaccine experts Friday recommended a full-scale human trial of the only existing approved Ebola vaccine to see if it offers cross-protection against a deadly strain spreading in the Democratic Republic of Congo.

The Ervebo vaccine has proved safe and effective against the more common Zaire strain of the Ebola virus, and World Health Organization experts said early data, notably from animal trials, showed it may also offer some protection against the rare Bundibugyo strain spreading rapidly in the DRC.

The recommendation came as the number of confirmed cases in the Democratic Republic of Congo surpassed 4,000, reaching 4,053, including 1,850 deaths.

WHO chief Tedros Adhanom Ghebreyesus warned again Friday that the virus was spreading faster than response efforts could keep up.

The U.N. health agency’s Technical Advisory Group on Candidate Vaccine Prioritization (TAG-CVP) for the Bundibugyo outbreak response met last week to review data that had emerged since its meeting in May, in the days following the outbreak declaration.

“The members recommended Ervebo, the only licensed Ebola vaccine, be prioritized for inclusion in a randomized clinical trial in the context of the ongoing outbreak,” a WHO statement said.

A spokesman told AFP it would be “a ring trial in the DRC,” involving the circle of contacts around known cases.

The experts looked at several studies, including one that showed three out of four nonhuman primates vaccinated with Ervebo survived Bundibugyo, compared with one out of four control animals.

They also looked at an unpublished study on ferrets that found the research-grade version of Ervebo provided 100% protection against Bundibugyo, whereas all control animals died within 10 days.

Tedros called the findings “good news.”

Managing expectations

The TAG-CVP experts unanimously agreed that there were no safety concerns about using Ervebo in a clinical research study vaccinating case contacts, noting that it is already licensed by regulatory agencies and has been given to hundreds of thousands of people in Africa.

“Expectations need to be managed about its likely protective effect if used in a Phase III ring vaccination trial as efficacy against symptomatic disease and transmission may not be high, whereas protection against a fatal outcome may be achieved,” their report said.

Final-stage Phase III trials of potential drugs or vaccines typically involve hundreds to thousands of people.

Nonetheless, a specific Bundibugyo vaccine remains the preferred option for fighting the current outbreak, they stressed.

Two potential Bundibugyo vaccines are in the early stages of clinical trials in humans, while a third is being developed to bring it to that stage.

Ebola is spread by contact with bodily fluids and causes a hemorrhagic fever.

Around 87% of cases in the DRC outbreak are in the northeastern Ituri province, with 11% in neighboring North Kivu.

Stockpile of doses

The Gavi global vaccine alliance maintains a stockpile of 500,000 Ervebo doses.

It said doses from the stockpile were to be made available for the trials, with some already in the DRC.

“This is already the largest Ebola outbreak in DRC’s history, and could well become the largest outbreak ever,” said Gavi chief executive Sania Nishtar.

“Given the terrible toll on communities and frontline workers, we are encouraged that the approved Ebola vaccine Ervebo … could help reduce severe illness and deaths.”

Gavi said around 55,000 frontline workers in Ituri and North Kivu have received Ervebo through previous preventive vaccination campaigns.