The Democratic Republic of Congo has secured an initial allocation of 70,000 doses of Merck’s Ervebo Ebola vaccine as health authorities intensify efforts to contain the country’s largest Ebola outbreak on record, while scientists prepare to test whether the vaccine can protect against the virus strain responsible for the current epidemic.

According to World Health Organization, the doses were released from the global Ebola virus disease vaccine stockpile following a request from the Congolese government last week.

The allocation comes as the country’s 17th Ebola epidemic continues to spread, with confirmed cases now exceeding 5,000 and the death toll reaching 2,378, according to government data.

The outbreak, which became the largest in the country’s history by case count is being driven by the Bundibugyo species of Ebola. Unlike the more commonly known Zaire ebolavirus, for which Ervebo is licensed and recommended, there are currently no approved vaccines or treatments specifically targeting the Bundibugyo virus.

Of the 70,000 doses allocated to the DRC, 20,000 will be used in a Phase 3 clinical trial designed to assess the potential impact of Ervebo against Bundibugyo virus disease.

The remaining 50,000 doses will be used to vaccinate frontline and health workers in accordance with current recommendations from the WHO Strategic Advisory Group of Experts on Immunization, known as SAGE.

WHO has stressed that Ervebo’s effectiveness against Bundibugyo virus in humans has not been established.

“It is not known whether Ervebo may be protective against the Bundibugyo virus in humans.”

Ervebo is licensed to prevent disease caused by Zaire ebolavirus, the strain associated with some of the world’s most severe Ebola outbreaks. The vaccine has played an important role in Ebola response efforts, particularly through vaccination strategies designed to protect people at high risk of exposure.

However, the scientific evidence surrounding its ability to protect against Bundibugyo remains limited.

According to WHO, early laboratory and animal studies suggest that Ervebo may provide some protection against the Bundibugyo virus. But evidence from humans is still lacking, making the Phase 3 trial a critical component of the current response.

The trial is expected to generate evidence that could help policymakers determine whether Ervebo can eventually be used more broadly against the virus.

Science and Urgency Collide Over Emergency Vaccination

DRC’s current Ebola crisis has placed enormous pressure on health authorities, communities and international partners as the number of infections and deaths continues to climb.

The current outbreak has already surpassed the previous record set during the 2018-2020 Ebola epidemic. That earlier outbreak, which affected eastern parts of the country, became one of the world’s longest and most complex Ebola emergencies.

The latest epidemic has again highlighted the challenges of controlling Ebola in communities where health systems face significant pressure and where public confidence and community participation can determine the success of containment measures.

Earlier this week, WHO Director-General Tedros Adhanom Ghebreyesus noted that the Ebola outbreak in eastern Congo remained a global emergency, reinforcing concerns over the potential for continued transmission and wider regional consequences.

The latest vaccine allocation is therefore intended not only to support immediate protection but also to strengthen the evidence base for future responses.

Africa CDC and WHO said they support the Congolese government’s focus on protecting the population while adopting a community-led approach. Such an approach seeks to give affected communities a central role in response activities, including disease surveillance, vaccination, treatment, risk communication and other public-health measures.

Moreover, WHO and Africa CDC indicated that, they were united in supporting the Congolese government to protect affected communities, save lives and bring the Bundibugyo outbreak to an end while generating scientific evidence needed to improve Africa’s preparedness for future epidemics.

The scientific component of the response could prove especially significant beyond the current emergency. Bundibugyo virus remains a less frequently encountered Ebola species than Zaire ebolavirus. The absence of an approved vaccine or treatment specifically targeting it leaves health authorities with fewer established medical tools when outbreaks occur.

If the Phase 3 trial demonstrates that Ervebo provides meaningful protection, the findings could influence future vaccination policies and potentially expand the options available to countries facing Bundibugyo outbreaks.

If the vaccine proves ineffective, the trial would nevertheless provide valuable evidence by helping researchers and policymakers understand its limitations and reinforcing the need to develop vaccines specifically designed to target the strain.