Why aren't the approved Ebola vaccines like Ervebo being used in the current DRC and Uganda outbreak?

The WHO has stated that there are no approved vaccines or therapeutics that could be of use to help contain the current outbreak, despite the existence of approved vaccines such as Ervebo (Merck & Co.) and a Johnson & Johnson Ebola vaccine, as well as two approved monoclonal antibody treatments — indicating that these existing tools are not effective against the specific Ebola virus strain causing the current outbreak.

What does the WHO's declaration of a public health emergency of international concern signify about the current Ebola outbreak?

On May 17, the WHO declared the Ebola outbreak in the Democratic Republic of the Congo (DRC) and Uganda a public health emergency of international concern, reporting at that time nearly 250 suspected cases and 80 suspected deaths, and warning that the actual number of cases may be considerably larger than reported by health agencies.

Why Won't Approved Ebola Vaccines Work for the Current Outbreak in DRC and Uganda?

May 20, 2026

The WHO declared an Ebola public health emergency in DRC and Uganda, noting that currently approved vaccines like Merck's Ervebo are ineffective against the new strain. Case counts continue to rise while available therapeutics fail to contain the outbreak.