A new experimental Ebola vaccine displayed 100 percent efficacy in a clinical trial involving thousands in Guinea, Africa, according to a new study published in The Lancet.
The trial included nearly 12,000 residents of Guinea. Among the 5,837 participants who received a vaccine, none contracted Ebola after 10 or more days. Vaccinated participants received regular follow-ups for 84 days. There were 23 Ebola cases among the thousands of others who were not immediately inoculated.
The 10-day marker is key as researchers implemented a "ring vaccination" technique, which includes communicating with everyone in the circle of family, friends, neighbors and caregivers upon detection of a confirmed case. Approximately half of these social circles were offered vaccine. No one who contracted Ebola within the first nine days post-vaccination were counted against the vaccine, because it was assumed they had already been infected prior to immunization.
"While these compelling results come too late for those who lost their lives during West Africa's Ebola epidemic, they show that when the next Ebola outbreak hits, we will not be defenseless," said Marie-Paule Kieny, PhD, the World Health Organization's assistant director-general for health systems and innovation and the study's lead author.
The trial was led by the WHO and the Guinean Health Ministry, Norway's Institute of Public Health and other institutions. The vaccine was manufactured by Kenilworth, N.J.-based Merck, which was previously granted Breakthrough Therapy Designation from the U.S. Food and Drug Administration.
From 1976 to 2014, controlling Ebola outbreaks was a time-consuming, expensive endeavor that required significant manpower. The success of this vaccine suggests these extensive endeavors may no longer be necessary in the event of future outbreaks. While the vaccine has not yet earned approval from any regulatory body, an emergency stockpile of 300,000 doses has been created to quell an outbreak should one flare up. The 2014 outbreak killed approximately 11,000 people in Africa.
The vaccine, however, is not perfect. It appears to work only against one of the two most common strains of Ebola and it is not clear how long the protection it offers will last. Adverse side effects reported with the vaccine were headaches (reported by 25.4 percent of those vaccinated), fatigue (18.9 percent) and muscle pain (13.7 percent).
"It's certainly good news with regard to any new outbreak — and one will occur somewhere," said Anthony Fauci, MD, director of the National Institute for Allergy and Infectious Diseases, according to The New York Times. "But we still need to continue working on Ebola vaccines."
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