A vaccine that went through early human testing in Kenya is set to play a new role in the Democratic Republic of Congo, where an Ebola outbreak has killed more than 2,000 people and spread across dozens of health zones.
The World Health Organization (WHO) and Africa Centres for Disease Control and Prevention (Africa CDC) have announced the release of 70,000 doses of Ervebo to support the DRC’s response to the outbreak.
The vaccine is being sent to the country at a time when health officials are dealing with an outbreak caused by the Bundibugyo virus, a strain for which there is currently no approved vaccine.
Kenya has a connection to Ervebo because one of the vaccine’s early trials was carried out in Kilifi at the Kenya Medical Research Institute (KEMRI)-Wellcome Trust research centre.
The vaccine was not created in Kenya. It came from a candidate known as rVSV-ZEBOV and was later manufactured by Merck.
Kenya was among several countries involved in human testing of the vaccine candidate before it was approved for protection against Zaire Ebola virus.
The Kenyan trial started in 2014, at a time when West Africa was dealing with a major Ebola outbreak.
At the KEMRI-CGMR Coast site in Kilifi, researchers planned to give the vaccine to 40 healthy adults, most of them health workers.
The study was designed to assess whether the vaccine was safe and whether it could trigger an immune response in those who received it.
The wider international research programme included clinical centres in Kenya, Gabon, Switzerland and Germany.
Results from the early studies showed that the vaccine triggered an immune response, while researchers did not report serious problems linked to the vaccine.
Further studies later showed that Ervebo could protect against Zaire Ebola virus.
The vaccine received WHO prequalification in 2019 and is now licensed for preventing disease caused by Zaire ebolavirus.
The situation in the DRC is different because the virus behind the current outbreak is Bundibugyo virus.
Ervebo is not specifically approved for protection against Bundibugyo virus, and WHO says it is still unclear whether the vaccine can prevent people from becoming infected with the strain.
Some laboratory and animal research has, however, provided early evidence that the vaccine may offer protection.
The planned vaccination exercise in the DRC will therefore serve another purpose beyond helping health workers and others at risk. It will allow researchers to gather information on whether Ervebo can protect people from Bundibugyo virus.
WHO and Africa CDC said 20,000 of the 70,000 doses will be used in a Phase 3 clinical trial.
Another 50,000 doses will go to frontline and health workers in line with recommendations from the WHO Strategic Advisory Group of Experts on Immunization (SAGE).
Health officials have also been told to make sure recipients understand that the vaccine’s protection against Bundibugyo virus has not been confirmed.
WHO and Africa CDC said participants in the trial and other people receiving the vaccine must be given clear information about its possible risks, benefits and limitations.
They must also give informed consent before receiving the vaccine.
The vaccine deployment comes as the scale of the DRC outbreak continues to grow.
By August 12, the country had recorded 4,665 confirmed Bundibugyo virus cases and 2,184 deaths.
The disease had reached 54 health zones in six provinces, prompting WHO to describe it as the biggest Ebola outbreak ever recorded in the DRC.
The current outbreak has now gone beyond the figures recorded during the 2018-2020 Ebola outbreak, which had 3,317 cases.
Neighbouring Uganda has also been affected by the outbreak.
WHO said Uganda declared its outbreak over in July after completing 42 days without recording a new case linked to local transmission.
Despite ending its outbreak, Uganda remains exposed to the risk of new infections because the virus continues to spread in neighbouring DRC.
The use of Ervebo in the DRC will therefore combine an immediate response for health and frontline workers with research aimed at answering a key question: whether a vaccine already proven against Zaire Ebola virus can also help protect people from Bundibugyo virus.