Merck Ebola vaccine posts 100% efficacy in PhIII

Merck's Ebola vaccine candidate is readied for Phase III trials in Sierra Leone.--Courtesy of CDC

Merck's ($MRK) Ebola vaccine, developed in tandem with NewLink Genetics ($NLNK) and tested in a novel "ring study," has protected 100% of patients from Ebola infection, according to interim results published in The Lancet on Friday.

In the aptly named "Ebola ça suffit," or "Ebola, that's enough," trial, all vaccinated individuals were protected against Ebola infection within 6 to 10 days of vaccination.

The trial, conducted by a team that includes researchers from the WHO, the Health Ministry of Guinea, and the Norwegian Institute of Public Health among others, is ongoing, with more than 4,000 patients having already received the jab.

The researchers forwent the traditional placebo-controlled trial and instead conducted a "ring study." The aim of such a study is to create a "ring" around Ebola cases to stop the spread of the virus. The team identified more than 7,000 people in Guinea at risk of infection and split them into two groups. Half would receive the vaccine, rVSV-ZEBOV, immediately after exposure to the virus, while the other half would be vaccinated after a delay. The immediate group reported no cases of Ebola after 10 days, while the other group reported 16 cases.

According to the abstract, the interim results might show that the vaccine confers protection very quickly and might be effective at the population level. As they continue the study, researchers are on the lookout for more data about the effectiveness of ring vaccination and its ability to protect communities via herd immunity.

Because of the waning number of Ebola cases in West Africa, makers of Ebola vaccines have been scrambling to find trial participants who are exposed enough to the disease to prove whether experimental vaccines actually ward off Ebola. GlaxoSmithKline ($GSK) and Johnson & Johnson ($JNJ) both have candidates in Phase II, while Novavax's ($NVAX) candidate recently reported top-line results from Phase I.

- here's the Lancet abstract
- read the release
- get FierceBiotech's take

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