A man in the Guinean capital Conakry receiving the experimental Ebola vaccine in April.

A highly unusual clinical trial in Guinea has shown for the first time that an Ebola vaccine protects people from the deadly virus. The study, published online today by The Lancet, shows that the injection offered contacts of Ebola cases 100% protection starting 10 days after they received a single shot of the vaccine, which is produced by Merck. Scientists say the vaccine could help to finally bring an end to the epidemic in West Africa, now more than 18 months old.

“This will go down in history as one of those hallmark public health efforts,” says Michael Osterholm, the director of the Center for Infectious Disease Research and Policy in Twin Cities, Minnesota, who wasn’t involved in the study. “We will teach about this in public health schools.”

“It’s a wonderful result and a fantastic illustration of how vaccines can be developed very quickly and can be used in an outbreak situation to control the disease,” says Adrian Hill, a vaccine researcher at the University of Oxford in the United Kingdom, also not involved in the work. Read More.

Published by sciencemag.org July 31, 2015