An experimental Ebola vaccine backed by the U.S. military has shown “robust” effectiveness in stopping the spread of the disease, a U.S. Army research lab announced Wednesday.

Researchers from Walter Reed Army Institute of Research and the National Institute of Allergy and Infectious Diseases (NIAID) began two phase 1 trials in October with 52 volunteers, 28 of who were administered the test vaccine while the rest were given a placebo. Ninety-three percent of the vaccinated group showed an improved antibody response within two weeks, priming their immune systems to fight off an Ebola infection. All of those vaccinated showed the response within a month.

“We saw a robust immune response following a single dose of the vaccine, which could be particularly useful in outbreak interventions,” Army Col. Stephen Thomas, one of the authors of the paper, said in a press release.

The vaccine, called VSV-ZEBOV, also underwent trials in Gabon, Kenya, Germany and Switzerland, which returned similar results, Reuters reported. The vaccine was developed by the Public Health Agency of Canada and licensed to NewLink Genetics Corp. and Merck & Co. Inc. It uses a modified version of the VSV cattle virus that had been engineered to carry Ebola genes, which could be used to test the Ebola antibody response without exposing participants to the deadly virus.

One of the previous trials was halted because participants developed pain in their hands and feet, leading to worries about possible side effects from the vaccine. However, the current trial did not produce any such results. "The most common side effects were injection site pain and transient fever that appeared and resolved within 12 to 36 hours after vaccination," NIAID said in a statement.

The results of the tests were published in the New England Journal of Medicine on Wednesday.

Ebola has infected over 25,000 people and caused over 10,000 deaths since the current outbreak began in West Africa in December 2013. There is currently no cure for the virus, but several countries are reporting a drop in the number of new cases, leading to hopes that the outbreak may be ending.