Merck takes its Ebola vaccine to Phase III in Sierra Leone

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

In the latest development in the race for an Ebola vaccine, Merck ($MRK) and partner NewLink ($NLNK) have taken their candidate to late-stage trials in Sierra Leone, the companies announced Tuesday.

The CDC, the Sierra Leone College of Medicine and Allied Health Sciences and the Sierra Leone Ministry of Health and Sanitation will lead the Phase III trial. It will involve 6,000 health and frontline workers in areas that were hit hard by the Ebola epidemic in the past few months, according to a CDC release. The candidate, rVSV-EBOV, is in Phase II/III trials in Liberia and Phase III trials in Guinea.

"We don't know whether this vaccine will be the Ebola prevention tool we're all eager for, but we hope that what we learn from (the trial) will help us save lives during this and future Ebola outbreaks," Anne Schuchat, M.D., Director of the CDC's National Center for Immunization and Respiratory Diseases, said in a statement.

When study participants enroll, they will be randomly assigned to two groups. One group will be vaccinated immediately and the other will be vaccinated 6 months later. The patients will be followed for 6 months, and the goal is to assess how well the vaccine works by comparing rates of Ebola disease in vaccinated individuals compared to those who haven't yet received the vaccine.

However, the CDC said in a statement that frontline workers who receive the vaccine should take full preventive actions against Ebola because it's not yet clear if the vaccine will protect against actual Ebola infection. And the epidemic is waning, with fewer new cases of Ebola reported as time goes on, which may impede the ability to determine whether the vaccine will work against an infection.

Merck and Newlink are not alone in the Ebola vaccine race. GlaxoSmithKline ($GSK) recently reported positive results from the Liberian Phase II trial of its candidate and that it may advance to Phase III. Merck also tested its jab in that trial. And Johnson & Johnson ($JNJ) announced in March that it was ready to start trialing its candidate in Ghana, Tanzania and Kenya. It is the third Ebola vaccine to be tested in humans.

- here's Merck/NewLink's release
- and here's the CDC release

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