A vaccine that was tested on volunteers in Kenya more than a decade ago is now being sent to the Democratic Republic of Congo as the country battles its largest Ebola outbreak.
The World Health Organization (WHO) and Africa Centres for Disease Control and Prevention (Africa CDC) said 70,000 doses of the Ervebo vaccine will be released to the DRC to help fight an outbreak caused by the Bundibugyo virus.
The vaccine is particularly significant for Kenya because one of its early human trials was conducted in Kilifi at the Kenya Medical Research Institute (KEMRI)-Wellcome Trust research centre.
However, Ervebo was not developed in Kenya. It was developed from a vaccine candidate known as rVSV-ZEBOV and was later manufactured by Merck. Kenya was one of the countries where the candidate was tested in humans before it was approved for use against Zaire Ebola virus.
The Kenyan trial began in 2014, during the major Ebola outbreak in West Africa.
Researchers at the KEMRI-CGMR Coast site in Kilifi planned to vaccinate 40 healthy adults, mainly health workers, to study the vaccine's safety and its ability to produce an immune response.
The wider international trials involved clinical centres in Kenya, Gabon, Switzerland and Germany.
Researchers found that the vaccine produced an immune response and that serious vaccine-related problems were not reported in the early trials.
The vaccine was later shown to protect against Zaire Ebola virus and received WHO prequalification in 2019. It is now licensed for prevention of disease caused by Zaire ebolavirus.
But there is an important difference in the current DRC outbreak.
The virus spreading in the DRC is Bundibugyo virus, not Zaire ebolavirus. There is currently no approved vaccine specifically for Bundibugyo virus disease. WHO says it is not yet known whether Ervebo protects people against this virus.
Laboratory and animal studies have given some early signs that the vaccine could offer protection. The new DRC vaccination programme will therefore also provide an opportunity to find out whether the vaccine can protect people against Bundibugyo virus.
Of the 70,000 doses being released, 20,000 will be used in a Phase 3 clinical trial. The remaining 50,000 will be offered to frontline and health workers under current recommendations from the WHO Strategic Advisory Group of Experts on Immunization (SAGE).
WHO and Africa CDC said people receiving the vaccine should be clearly informed that its benefits against Bundibugyo virus are not yet proven.
They said people taking part in the trial and others receiving the vaccine must understand its possible risks, benefits and limitations and give informed consent.
The decision comes as the DRC faces a rapidly growing outbreak.
As of August 12, the DRC had reported 4,665 confirmed Bundibugyo virus cases and 2,184 deaths.
Cases had spread to 54 health zones in six provinces. WHO said this had made the outbreak the largest Ebola outbreak ever recorded in the country, surpassing the 2018-2020 outbreak, which recorded 3,317 cases.
The outbreak has also affected Uganda. WHO says Uganda declared its outbreak over in July after going 42 days without a new locally transmitted case, but the country remains at risk because of continued transmission in neighbouring DRC.
Gavi, the Vaccine Alliance, is providing US$7 million to fund the shipment of the 70,000 vaccine doses.
Gavi CEO Dr Sania Nishtar said; “This new funding will help save lives, keep other deadly diseases at bay and support the rollout of the Ervebo vaccine, which has shown promising signs in early data of offering protection against Bundibugyo.”
“Given the severity of this outbreak, it is important every tool we have is brought to bear to prevent loss of life and ease suffering.”
Gavi is also providing another US$6 million to help keep routine vaccination services running in affected parts of the DRC and prepare for possible Ebola vaccination.
About US$4 million of this money will help maintain routine immunisation for more than 1.17 million children under two in five provinces.
This is important because previous Ebola outbreaks disrupted normal vaccination services, leaving children exposed to diseases such as measles.
The global Ebola vaccine stockpile was created after the 2014-2016 West African Ebola epidemic, when no approved Ebola vaccine was available. It now holds about 500,000 Ervebo doses and can provide vaccines to countries facing outbreaks.
Kenya has also been part of the wider preventive use of Ervebo. WHO and Gavi say 167,000 doses have been used in preventive campaigns for health and frontline workers in DRC, Guinea-Bissau, Kenya, Sierra Leone and Uganda since the global stockpile system was established.
For Kenya, the DRC response is a reminder of the country's role in developing and testing tools used against dangerous diseases in Africa. The vaccine now being deployed in the DRC began its journey to becoming an approved Ebola vaccine through clinical research that included volunteers and researchers in Kilifi.
The immediate question, however, is whether a vaccine proven against Zaire Ebola can also help against Bundibugyo virus. The Phase 3 trial in the DRC is expected to provide some of the strongest evidence yet to answer that question.
