An Ebola vaccine has demonstrated 100 percent efficacy in a large-scale human trial, according to a study published Friday in U.K.-based medical journal The Lancet.
The vaccine successfully prevented nearly 6,000 people from contracting the disease, deemed by the World Health Organization as "one of the most lethal known pathogens".
Produced by U.S. pharmaceutical company Merck Sharp & Dohme, the rVSV-ZEBOV vaccine was trialed on close to 12,000 people in the west African country of Guinea. Of the 5,837 people who received the vaccine, none contracted Ebola 10 or more days after their vaccination. By contrast, 23 cases were recorded among those who did not receive the vaccine in the same time frame, set to allow for the disease's incubation period.
The trial took place in 2015 and was led by WHO, working alongside with Guinea's Ministry of Health, Medicins sans Frontiers and the Norwegian Institute of Public Health, with other international collaborators.
Dr Marie-Paule Kieny, WHO's assistant director-general for health systems and innovation, described the news as "compelling" in a press statement, adding that should Ebola break out again, "we will not be defenceless."
Ebola killed more than 11,300 people in west Africa during its 2013-2016 outbreak, according to WHO's press release. The rVSV-ZEBOV vaccine does not treat those already suffering from the disease, but rather prevents its transmission.
The vaccine does not contain any live Ebola virus. Its trial used a so-called "ring vaccination" method – the same technique that helped eradicate small pox. Researchers contacted all those known to have come into contact with an infected person in the three weeks prior to his/her diagnosis. These people then received the vaccine.
Funding from the Global Alliance for Vaccines (GAVI) was given to Merck in January towards future procurement of the vaccine once it is approved by WHO. Part of GAVI's agreement with Merck means that 300,000 doses of the vaccine will be available for emergency use before this time.
"Ebola left a devastating legacy in our country," said Dr Sakoba Keita, coordinator of Guinea's Ebola response, said in WHO's statement. She also described her pride in helping develop a vaccine that will "prevent other nations from enduring what we endured."