The Democratic Republic of Congo has begun vaccinating frontline health workers against Ebola as authorities intensify efforts to contain an outbreak that has expanded to 60 health zones across six provinces.
The vaccination campaign began in Kisangani, the capital of Tshopo Province, on August 27, with healthcare workers and other people directly involved in the Ebola response among those being prioritised.
But the rollout comes with a major scientific uncertainty: the Ervebo vaccine being used is licensed against the Zaire strain of Ebola, while the current outbreak is being caused by the Bundibugyo virus.
The World Health Organization said the vaccine’s ability to protect people against Bundibugyo virus has not yet been established in humans. WHO’s latest Ebola outbreak update
The outbreak is moving faster
The scale of the crisis has continued to grow rapidly.
According to the latest WHO situation report, dated August 28 and based on data through August 26, Congo had recorded 5,794 confirmed cases and 2,786 deaths, giving the outbreak a crude case-fatality ratio of 48.1 percent.
The outbreak has spread across 60 health zones in six provinces: Ituri, North Kivu, South Kivu, Haut-Uélé, Tshopo and Bas-Uélé.
Ituri remains the epicentre, accounting for 4,802 confirmed cases, while North Kivu has recorded 775 cases.
Two additional health zones, Biena and Manguredjipa in North Kivu were among the latest areas to report cases.
The WHO has described the continuing transmission and geographic expansion as a very high risk within Congo, while warning that the possibility of further regional spread remains.
Why use a vaccine that was developed for another strain?
The decision to deploy Ervebo reflects the limited options available to health authorities.
There is currently no licensed vaccine or specific treatment for Bundibugyo virus disease. The current campaign is therefore being conducted alongside research intended to determine whether Ervebo can provide some protection against the strain responsible for the outbreak.
WHO and Africa CDC previously supported the allocation of 70,000 Ervebo doses to Congo. Of those, 50,000 were allocated for frontline and healthcare workers, while 20,000 were designated for a Phase 3 clinical trial examining the vaccine’s potential against Bundibugyo virus.
The vaccination programme is being conducted under a compassionate-use framework, meaning the vaccine is being used in response to a serious public health emergency even though its effectiveness against the specific virus circulating in Congo has not been established.
That makes the campaign both a public-health intervention and an opportunity to gather evidence that could influence how future outbreaks are managed.
The bigger problem is not just the virus
Containing the outbreak is proving difficult because Ebola is spreading in communities already affected by insecurity, displacement and weak access to healthcare.
WHO says more than 26 million people in Congo face acute food insecurity, while about one million internally displaced people are living in Ituri Province alone.
Armed violence and insecurity have restricted access for response teams, while population movement makes contact tracing and surveillance more difficult.
The outbreak is also affecting essential healthcare beyond Ebola.
UNICEF previously reported that the use of essential health services in the main outbreak hotspots fell by 42 percent between April and June as fear of infection and disruption kept children and families away from healthcare facilities.
That means the consequences of the outbreak extend beyond the people who contract Ebola.
Routine vaccinations, maternal healthcare and other essential services can also suffer when communities lose confidence in health facilities or when medical workers and response teams cannot safely reach affected areas.
A growing regional concern
The expansion of the outbreak is particularly significant for neighbouring countries.
WHO says the continuing intensity of transmission in Congo means there remains a risk of the virus being exported across international borders.
Uganda, which shares a border with Congo, recently completed the required 42-day monitoring period after recording its own Ebola outbreak. WHO says cross-border surveillance and preparedness remain essential because people continue to move through both formal and informal border routes.
The concern is therefore no longer limited to whether Congo can contain the outbreak within its affected communities.
The bigger question is whether the combination of vaccination, contact tracing, treatment capacity and cross-border surveillance can slow transmission before the virus reaches more populations.
What happens next?
The immediate focus will be on protecting healthcare and frontline workers while collecting evidence on how well Ervebo performs against Bundibugyo virus.
At the same time, health authorities and researchers are continuing work on vaccines and treatments specifically targeting the current strain.
For Congo, however, science is only one part of the battle.
The response will also depend on whether health teams can reach communities safely, identify cases quickly, maintain contact tracing and convince people to seek care without fear.
With the outbreak already spanning 60 health zones, the success of the vaccination campaign may ultimately depend as much on the strength of the wider public-health response as on the vaccine itself.
