Merck's experimental Ebola vaccine poised for emergency use in Congo outbreak

The Democratic Republic of the Congo has given initial approval for the emergency use of Merck’s as-yet-unlicensed Ebola shot to combat a local outbreak, and medical providers are putting together plans for administering it.

"The non-objection was given," Congo Health Ministry spokesman Jonathan Simba told Reuters by telephone. "Now there's a Médecins Sans Frontières team that is arriving today to validate the protocol with the technical teams."

A Merck spokeswoman told FiercePharma that the company "stands ready to ship our investigational vaccine … if and when the DR Congo government decides to implement vaccination," and said that the WHO will be providing advice very soon. 

To ensure a supply during an outbreak, Merck reached an agreement with international vaccine alliance Gavi last January, creating a stockpile of 300,000 doses for emergency use. The company has now amassed 500,000 doses, according to the spokeswoman.

Merck’s candidate, known as rVSV-ZEBOV, showed a 100% protection rate during a phase 3 trial in Guinea, where 5,837 subjects who used the shot were not infected 10 days after immunization. How long its benefits can last is as yet unclear.

The work on vaccination protocols comes as Congo combats an outbreak that was identified May 12 in the northern part of the country bordering the Central African Republic. As of last week, the local health department has registered 52 suspected cases. Two of those cases have been confirmed so far. WHO spokesman in Congo Eugene Kabambi told Reuters that the situation appears to be under control.

The vaccine isn't yet approved by drug regulators. However, during a WHO advisory committee meeting about a month ago, the organization recommended that Merck’s shot "be promptly deployed under the Expanded Access framework" if an Ebola outbreak were to occur.

The Congo government will soon decide how to deploy the vaccine, though it could be a challenge to store and transport the shot to a remote region under required cold-chain conditions. The outbreak is centered in the Likati Health Zone, 800 miles northeast of the country’s capital, and the vaccine must be stored at -70°C (-94°F) or below. It is stable for only one week at 4°C (39°F).

The vaccine received Breakthrough Therapy Designation from the FDA and Priority Medicines status from the EMA. The company is "in the process of assembling the critical components required for licensure," and expects to file for a license this year, the spokeswoman said.