Geneva, Aug 7 (V7N) - WHO vaccine experts have recommended a full-scale human trial of the only existing approved Ebola vaccine to see if it offers cross-protection against the strain spreading in the Democratic Republic of Congo.

The Ervebo vaccine has proven safe and effective against the more common Zaire strain of Ebola virus. WHO experts said early data, notably from animal trials, showed it may offer some cross-protection against the rare Bundibugyo strain now surging in the DRC.

The recommendation came as confirmed cases in the DRC reached 4,053, including 1,850 fatalities. WHO officials have repeatedly warned that the virus is spreading faster than response efforts can keep up.

The WHO's technical advisory group on candidate vaccine prioritisation (TAG-CVP) reviewed new data since their May meeting and recommended that Ervebo be prioritized for inclusion in a randomized clinical trial during the ongoing outbreak.

Experts reviewed several studies, including one where three out of four non-human primates vaccinated with Ervebo survived Bundibugyo, compared with one out of four in the control group. Another unpublished study on ferrets found that the research-grade version of Ervebo provided 100 percent protection against Bundibugyo, while all control animals died within 10 days.

The experts unanimously agreed there were no safety concerns about using Ervebo in clinical research, noting it is already licensed and has been given to hundreds of thousands of people in Africa. However, they cautioned that "expectations need to be managed" about its protective effect, as efficacy against symptomatic disease and transmission may not be high, though protection against fatal outcomes may be achieved.

Given the wealth of data, Ervebo "could enter a Phase III trial without an initial Phase II evaluation," the experts said. Still, they stressed that a specific Bundibugyo vaccine remains the preferred option for fighting the current outbreak. Two potential Bundibugyo vaccines are in early-stage clinical trials, with a third being developed.

Ebola, spread through contact with bodily fluids, causes haemorrhagic fever and has killed over 15,000 people in Africa in the past 50 years. The case fatality rate in the DRC outbreak is currently 46 percent.

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