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The World Health Organization and outside experts are making arrangements to send an experimental Ebola vaccine to the Democratic Republic of Congo, should officials there say they need it to quell an outbreak there.

The DRC has not yet formally requested the vaccine, and it’s unclear if or when it will. The country’s drug regulatory agency would also have to authorize emergency use of the vaccine, which is not yet licensed.


But the WHO and Gavi, the Vaccine Alliance, told STAT that preparations to have the experimental vaccine ready for use are being made on a parallel track with investigations in DRC into the scale of the outbreak.

“If the question is: Is it going to be used in this particular outbreak? It’s not clear yet,” said Dr. Seth Berkley, CEO of Gavi, a public-private partnership that provides vaccines to lower income countries.

“That being said, everything is being put in place to use the vaccine if it is requested or if it turns out the need accelerates.”


The outbreak, reported to the WHO last week, has grown to 20 suspected cases. Three of the infected have died.

This Ebola epidemic, the country’s eighth, is in a remote part of northern DCR, a province called Bas-Uele. It is a part of the country with few roads, which should help contain the epidemic. The three previous Ebola outbreaks in DRC involved dozens of cases as opposed to hundreds or thousands.

But the location also creates logistical difficulties. Transporting medical supplies and teams of investigators to the outbreak zone is slow work — as is getting patient samples back to the capital, Kinshasa, for testing.

It will also be challenging to get doses of vaccine to the area if the government decides to use it. The experimental Ebola vaccine must be stored at -80 Celsius, which would involve transporting it in freezers.

The vaccine, which goes by the working name rVSV-ZEBOV, is being developed by pharmaceutical giant Merck. Although there are other experimental Ebola vaccines at various stages of development, this is the only one so far which has been shown to protect people from the deadly virus.

That evidence comes from a clinical trial conducted in Guinea during the West African Ebola outbreak of 2014-2015. The trial showed the vaccine induced quick protection, a desirable characteristic for a vaccine designed for use in controlling outbreaks.

That study used what is known as a ring vaccination design, in which people who had been in contact with a confirmed case were vaccinated to prevent ongoing spread. The WHO has said if DRC uses the Ebola vaccine, it should vaccinate using the ring technique, said Tarik Jašarević, a spokesman for the WHO.

In an agreement with Gavi, Merck is required to have on hand at all times at least 300,000 doses of the Ebola vaccine. There is also currently a small number of doses — around 800 or 1,000 — in Geneva, Berkley said.

A spokeswoman for Merck said the company is in contact with WHO, Doctors without Borders — which has sent a response team to the outbreak site — and other organizations about the outbreak.

“We stand ready to ship our investigational vaccine for Ebola Zaire … once appropriate approvals are in place,” she said in an email.

Berkley pointed out that because the vaccine has not yet been licensed, there are regulatory hurdles to clear before it can be used, and that can take some time.

“It’s a little different than yellow fever vaccine, which can be stored in different places and used as a clinical vaccine pretty indiscriminately. There are some complexities with using this,” Berkley said.

So will this outbreak be the first in history where Ebola vaccine is used to help stamp out transmission? It’s too soon to say, he said.

“To be honest with you, I would hope that the epidemic would be over so quickly and there would be so few deaths that there would be no need to use it,” Berkley said.

“That’s the best-case scenario for everybody,” he said. “Of course, if the outbreak goes further or there’s an opportunity to use it, I would like to make sure we don’t have another large outbreak and that it does get used.”