What is the primary purpose of the Phase 3 trial for Merck's Ebola vaccine Ervebo in the DRC?

The primary purpose of the Phase 3 trial is to evaluate whether Ervebo — which is already approved for use against Orthoebolavirus zairense — is effective in humans against the Bundibugyo virus (Orthoebolavirus bundibugyoense), a related but rarer species now circulating in the DRC and not previously assessed for Ervebo's efficacy.

How many doses of Ervebo are being used in the Phase 3 trial, and how are the remaining doses allocated?

Twenty thousand doses of Ervebo have been allocated specifically for the Phase 3 clinical trial, while the remaining 50,000 doses will be administered to frontline health workers in the DRC.

Ebola Vaccine Enters Phase 3 Trial. Will It Work on a New Target?

Aug 20, 2026

The WHO announced 70,000 doses of Merck's Ervebo vaccine have reached the DRC for a Phase 3 trial targeting the Bundibugyo virus strain. This study aims to evaluate effectiveness against the newly circulating species beyond the currently approved Zairense.