Beginning in 2014, the largest recorded outbreak of Ebola hemorrhagic fever spread across West Africa, infecting over 27,000 people in Guinea, Sierra Leone, and Liberia, with additional cases in other countries due to travel. There have been over 11,000 deaths in this outbreak — a 40 percent mortality rate.
The global healthcare community sprang into action, setting up quarantines and medical care facilities in areas that did not have the infrastructure to handle the crisis.
All of the efforts to manage the outbreak are paying off, with some long-awaited happy news. According to a new study published in The Lancet, a clinical trial for an Ebola vaccine known as VSV-EBOV has been shown to be 100 percent effective under certain conditions. The trial took place between March 23 and July 20 of 2015.
The vaccine trial used over 4,000 participants, who were randomized into two groups.
Conventional vaccine trials would give half of the people a placebo, but given the dire nature of the outbreak, everyone received the active vaccine, although not at the same time.
This trial used the "ring" approach, which means that those who cared for or were around someone who had fallen ill were treated. By "encircling" the patient with immunized caregivers, it would ideally curb the spread of infection.
One group received the vaccination immediately, while the other group waited 3 weeks after a patient had been confirmed to have Ebola. Out of the 2,380 individuals who had to wait to receive the vaccine, there were only 16 confirmed cases of ebola infection.
The group of 2,014 individuals who were given the vaccine right away? Not a single case of Ebola infection.
Part of what makes this vaccine so successful is the virus itself.
Some viruses, like HIV and the flu, have a high mutation rate, evolving rapidly with every generation. This quickly-moving target makes it extremely difficult for scientists to develop vaccines. By the time they've developed a good way to target the virus, it has evolved enough so the treatment isn't very effective.
Ebola is different, which is a good thing.
Ebola is a relatively simple virus, with only seven genes that have a relatively low mutation rate. It was essentially a sitting duck for scientists to get in the crosshairs and attack.
If the results hold up, this could help stop future outbreaks from reaching the devastating levels that were seen in this current outbreak.
When an individual is diagnosed with Ebola, the caregivers can receive the vaccine, keeping the virus from spreading, just as it was done in this trial.
"This is an extremely promising development," Margaret Chan, who serves as Director-General of the World Health Organization, said in a news conference. "The credit goes to the Guinean Government, the people living in the communities and our partners in this project. An effective vaccine will be another very important tool for both current and future Ebola outbreaks."
There is still work to be done in developing this vaccine further, as this is an early, yet important, indicator of the vaccine's performance. As of July 26, there will be no more randomization, and none of the participants will be asked to wait three weeks.
A separate trial is also being conducted with those who work on the front lines of the Ebola treatment facilities and experience the most exposure.
While it is possible for the efficacy rate to drop below 100 percent in future trials, it is hoped that the rate will still be high enough to prevent such a widespread and deadly outbreak from ever happening again.