Response to Merck's Ebola vaccine lasts at least a year, study finds

In a phase 3 trial in West Africa, Merck’s Ebola vaccine rVSV-ZEBOV has already shown it can elicit a quick immune response. Now, a new study in the U.S. found that the vaccine's protective qualities can last for at least a year.

A team of scientists from Merck and partner NewLink Genetics conducted a phase 1b trial at eight U.S. study sites on 512 healthy adults. All seven doses produced a robust antibody response, according to the investigators, and neutralizing antibodies persisted for at least a year after immunization.

The team published the results in The Lancet Infectious Diseases.

Adverse events included joint pain and headache, but most were mild to moderate and passed quickly. Based on the results, the team confirmed the selection of the 2 x 107 plaque-forming-unit dose used in the previous phase 3 outbreak clinical trial.

In that 7,651-participant "ring vaccination" trial, Merck's shot protected 100% of vaccinated subjects from Ebola infection within 6 to 10 days, interim results showed; full results are expected later this year.

While Merck hasn't yet submitted its shot to regulatory agencies, health officials have considered using the vaccine to combat a recent Ebola outbreak detected in the Democratic Republic of the Congo. Local health authorities approved rVSV-ZEBOV for emergency use under trial settings, but the government is holding off on deploying the experimental vaccine and deployment is not yet advised by the World Health Organization, according to the Wall Street Journal.

Earlier this month, a Doctors Without Borders spokesperson said preparations for vaccination are underway "in order to rapidly initiate a ring vaccination should an [Ebola virus disease] laboratory confirmed case be identified outside of the already defined contacts."

Merck has said it will submit its vaccine for approval by the end of 2017.