WHO experts urge trial of Ebola vaccine against Bundibugyo strain

World Health Organization (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 current outbreak in the Democratic Republic of Congo (DR Congo).

The recommendation concerns Ervebo, a vaccine proven 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 currently exists.

The WHO's Technical Advisory Group on Candidate Vaccine Prioritization (TAG-CVP) reviewed emerging evidence and recommended that Ervebo be prioritized for inclusion in a randomized clinical trial during the ongoing 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 An unpublished ferret study found that a research-grade version of the vaccine provided complete protection, while all unvaccinated animals died within 10 days.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 already 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 percent.

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 already in early-stage human trials, while a third candidate is being developed.

The current outbreak is the DR Congo's 17th since Ebola was first identified in 1976. The virus spreads through contact with infected bodily fluids and can cause severe haemorrhagic fever.