WHO faces complex vaccine and security questions in Ebola response in Congo

Depending on the strain of the virus causing Congo's current outbreak, the Merck vaccine used to stem the country's previous one may not be effective.

New outbreak comes days after another one declared over

A World Health Organization worker administers a vaccination during the previous Ebola outbreak in Congo in May. Officials will not know whether the vaccine will work in the current outbreak until they confirm what strain of Ebola they're dealing with. (Kenny Katombe/Reuters)

An Ebola outbreak in eastern Democratic Republic of Congo is likely spread over tens of kilometres and poses a high regional risk given its proximity to borders, a World Health Organization (WHO) official said on Thursday.

Four people have tested positive for Ebola in and around Mangina, a town of about 60,000 people in North Kivu province, 100 kilometres from the Ugandan border, the health ministry said.

Another 20 people died from unidentified hemorrhagic fevers in the area, mostly in the second half of July.

News of the outbreak emerged just days after a previous outbreak on the other side of the Central African country that killed 33 people was declared over.

It will be complicated and perhaps impossible to use a vaccine to tackle the new Ebola outbreak, WHO's emergency response chief said on Thursday.

Almost 20 WHO officials were already on their way to the epicentre, Peter Salama told Reuters at WHO's headquarters in Geneva.

Officials have not yet confirmed which type of Ebola is causing the outbreak. That information, expected within days, is crucial for the vaccine strategy.

It could be the Zaire, Sudan or Bundibugyo strain of Ebola, Salama said, although the high death rate pointed toward Zaire, the same kind of Ebola that caused Congo's last outbreak, which was declared over just last week.

That effort relied heavily on a vaccine by Merck, which was given to contacts of Ebola patients, and contacts of contacts, to ring-fence the disease and stop it spreading.

"If this [outbreak] turns out to be Ebola Zaire, then certainly that would bring that option into play," Salama said. "If it doesn't we are going to have to look at much more complex options, and we may not have any vaccine options."

Merck's vaccine is only effective against the Zaire strain, and is the only vaccine that has gone through Phase 3 efficacy trials, a spokesman for the GAVI global vaccine alliance said.

Another vaccine is being developed by Johnson & Johnson to protect against multiple related diseases, including 
the Sudan strain.

"However it has not been through Phase 3 and it would have to be deployed as part of a clinical trial," the GAVI spokesman said. "While it is promising, we do not yet have reliable data on its efficacy."

A World Health Organization staffer holds a used vial of Ebola vaccine in Congo in May. For the first time since the Ebola virus was identified, a vaccine was dispatched to front line health workers. However, it is not effective with every strain of the virus. (Sam Mednick/Associated Press)

Ring-vaccination depends on tracing all potential Ebola sufferers, which might be impossible in northeast Congo, where Salama said there were over 100 armed groups. Instead, WHO might consider "a more homogenous geographical strategy," he said.

Security concerns will be assessed on a day-to-day-basis and may oblige WHO to hold staff back in the cities of Goma and Kinshasa until their safety can be assured, he said.

Armoured personnel carriers and support from United Nations peacekeepers may be needed, making it very difficult to deploy the kind of far-reaching contact tracing used in the previous outbreak.

WHO dealt with an outbreak in the same area around a decade ago, "where we had to negotiate with many armed factions," Salama said.

"So there is experience in the organization. That's not to say this is going to be simple."