World Health Organisation (WHO) vaccine experts have recommended a full-scale human trial to assess whether the only licensed Ebola vaccine can protect against the Bundibugyo strain driving the outbreak in the Democratic Republic of Congo (DRC).
The recommendation concerns Ervebo, a vaccine proved effective against the Zaire strain of Ebola. Early research, including studies in animals, suggests it could provide some protection against Bundibugyo, a rarer strain for which no approved vaccine exists.
The WHO’s Technical Advisory Group on Candidate Vaccine Prioritisation (TAG-CVP) reviewed emerging evidence and recommended that Ervebo be prioritised for inclusion in a randomised clinical trial during the outbreak.
In one study involving non-human primates, three of four animals vaccinated with Ervebo survived exposure to Bundibugyo, compared with one of four in the control group. An unpublished ferret study found that a research-grade version of the vaccine provided complete protection, while all unvaccinated animals died within 10 days.
The experts said there were no safety concerns about testing Ervebo in a clinical study involving contacts of Ebola patients. The vaccine has been administered to hundreds of thousands of people in Africa.
However, WHO cautioned that its effectiveness against the Bundibugyo strain remains uncertain.
The advisory group said protection against symptomatic infection and transmission could be limited, although the vaccine may reduce the risk of death.
According to the latest figures cited by the WHO, confirmed cases have reached 4 053, including 1 850 deaths, putting the case fatality rate at about 46%.
WHO officials have repeatedly warned that the virus is spreading faster than response efforts can keep pace.
Two potential vaccines specifically targeting the Bundibugyo strain are in early-stage human trials, while a third candidate is being developed.
The outbreak is the DRC’s 17th since Ebola was first identified in 1976. The virus spreads through contact with infected bodily fluids and can cause severe haemorrhagic fever.
- WHO vaccine experts have recommended a full-scale human trial to test the Ervebo vaccine against the Bundibugyo strain of Ebola in the DRC outbreak.
- Ervebo is licensed and proven effective against the Zaire Ebola strain but has uncertain effectiveness against the Bundibugyo strain.
- Animal studies showed Ervebo provided significant protection against Bundibugyo, with survival in primates and complete protection in ferrets.
- WHO reported 4,053 confirmed Ebola cases and 1,850 deaths in the current DRC outbreak, with a case fatality rate of about 46%.
- Two vaccines targeting Bundibugyo are in early human trials, and a third candidate vaccine is in development.
