An experimental Ebola vaccine manufactured by Merck & Co. was found to be highly protective against the deadly virus, showing promise in the fight against future outbreaks after an earlier epidemic killed thousands and highlighted a shortage of weapons to battle the disease.

The vaccine was studied in a trial involving more than 11,000 people in Guinea. Of those who received the shot in a final-stage trial, no Ebola cases were recorded after a ten-day incubation period, according to a study published in the medical journal, the Lancet.

The outbreak of Ebola from 2013 to 2016 triggered a public health crisis in West Africa, resulting in more than 11,300 deaths, primarily in Liberia, Sierra Leone and Guinea. It also exposed holes in global infectious disease preparedness, with infected travellers reaching as far away as Texas.