The Ebola outbreak in West Africa continues to stymie world health experts as the death toll rises to 1,552. The World Health Organization recently warned that the deadly virus might infect as many as 20,000 people over the next several months. The difficulty in managing the outbreak has prompted accelerated efforts toward the development of vaccines and treatments.

Researchers at the National Institutes of Health, in partnership with pharmaceutical giant GlaxoSmithKline, are planning to begin testing a candidate vaccine for the Ebola virus this week. The testing will take place at the NIH Clinical Center in Bethesda, Maryland.

“There is an urgent need for a protective Ebola vaccine, and it is important to establish that a vaccine is safe and spurs the immune system to react in a way necessary to protect against infection,” Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases at the NIH, said in a statement.

The vaccine being tested at the NIH is different from the experimental Ebola treatment drug called ZMapp. Two Americans received ZMapp last month, a drug that is designed to treat rather than prevent Ebola illness.

According to Fauci, the candidate vaccine has “performed extremely well” in primate studies but has not yet been tested in humans. The phase I study scheduled to begin this week will involve 20 subjects aged 18 to 50 and will focus on safety. The target outcome of the study is a measurable immune response necessary to protect against Ebola. None of the subjects will be infected with Ebola virus.

In addition, a $4.7 million grant will fund Ebola vaccine trials this month at the University of Oxford in the U.K. as well as centers in Gambia and Mali, according to sources at GlaxoSmithKline. The vaccine will be tested in a total of 140 patients.

Ebola virus was first discovered almost four decades ago but is so rare in humans that drug companies had no incentive to develop vaccines or treatments. GlaxoSmithKline bought the Swiss vaccine company Okairos AG in 2013, which had been working with the NIH on a vaccine since 2011. Results from phase I testing this month are expected before the end of the year and could mean a marketable vaccine sometime in late 2015.

Meanwhile, the Iowa pharmaceutical company NewLink Genetics Corp, in partnership with the U.S. Department of Defense, is planning to begin testing a different vaccine in human subjects at the Walter Reed Army Institute of Research in Silver Spring, Maryland.