Ebola vaccine works, study shows



An experimental Ebola vaccine completely protected people from the killer virus at the end of the west African epidemic, researchers report.

They used the same strategy that was used to eradicate smallpox in the 1970s. Called ring vaccination, it calls for vaccinating people who have been in contact with patients, and contacts of contacts.

It worked, the team led by the World Health Organization found.

"Vaccine efficacy was 100 percent," they wrote in their report, published in Friday's issue of the Lancet medical journal.

More on the Ebola epidemic

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West Point slum in Liberia still struggling after Ebola epidemic
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West Point slum in Liberia still struggling after Ebola epidemic
MONROVIA, LIBERIA - FEBRUARY 09: Children bathe in a bucket in the West Point slum on February 9, 2016 in Monrovia, Liberia. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 10: A restaurant sits empty overlooking the West Point slum on February 10, 2016 in Monrovia, Liberia. Monrovia was hard hit by the Ebola epidemic and the economy has not recovered. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 10: A water tank for washing hands stands in front of a municipal center in the West Point slum on February 10, 2016 in Monrovia, Liberia. The school was cleaned and refurbished following the epidemic. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 10: Members of the opposition Congress for Democratic Change party protest in the West Point slum on February 10, 2016 in Monrovia, Liberia. West Point was hard hit by the Ebola outbreak and remains one of the most impoverished communities in Liberia. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 10: Children play basketball in front of a school, formerly an Ebola center, in the West Point slum on February 10, 2016 in Monrovia, Liberia. The school was cleaned and refurbished following the epidemic. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 09: A child stands atop a sandbag made from a former sack of American food aid sent to the West Point slum on February 9, 2016 in Monrovia, Liberia. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 09: A man smooths out streetside posters in the West Point slum on February 9, 2016 in Monrovia, Liberia. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 09: The Liberian flag flies in front of a school formerly used as an Ebola holding center in the West Point slum on February 9, 2016 in Monrovia, Liberia. In August of 2014 the center was overrun by a mob, who claimed that the Ebola epidemic was a hoax. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak, and health facilities at the time were overwhelmed. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 09: People pray during a seaside church service in the West Point slum on February 9, 2016 in Monrovia, Liberia. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 09: Boys show off their new puppies in the West Point slum on February 9, 2016 in Monrovia, Liberia. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 09: People pray during a seaside church service in the West Point slum on February 9, 2016 in Monrovia, Liberia. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 09: Fish dry as children play in the West Point slum on February 9, 2016 in Monrovia, Liberia. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 09: A woman and her child pass by an internet cafe in the West Point slum on February 9, 2016 in Monrovia, Liberia. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 09: Women walk through the refuge-strewn shorline of the West Point slum on February 9, 2016 in Monrovia, Liberia. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 09: Women dance during a church service on the beach in the West Point slum on February 9, 2016 in Monrovia, Liberia. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak. After almost two years, the World Health Organization this January 14 declared the epidemic over, after it killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 09: Children stand outside a cinema in the West Point slum on February 9, 2016 in Monrovia, Liberia. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 09: A caretaker stands in a classroom, empty of students while on a school vacation, in school formerly used as an Ebola holding center in the West Point slum on February 9, 2016 in Monrovia, Liberia. In August of 2014 the center was overran and patients sick with Ebola were removed by a mob, who claimed that the Ebola epidemic was a hoax. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak, and health facilities at the time were overwhelmed. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 09: A man rests in the afternoon heat at his sidewalk clothing stand in the West Point slum on February 9, 2016 in Monrovia, Liberia. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 09: Chidren play on the beach of the West Point slum on February 9, 2016 in Monrovia, Liberia. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 09: Ebola survivor Banganelee Yougi, 22, smiles while passing a market in the West Point slum on February 9, 2016 in Monrovia, Liberia. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 09: Caretakers eat lunch at the entrance of a school formerly used as an Ebola holding center in the West Point slum on February 9, 2016 in Monrovia, Liberia. In August of 2014 the center was overrun by a mob, who claimed that the Ebola epidemic was a hoax. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak, and health facilities at the time were overwhelmed. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 09: Women walk with their wares through the West Point slum on February 9, 2016 in Monrovia, Liberia. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak, and health facilities at the time were overwhelmed. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 09: Boys carry wood for construction along the refuge-strewn shorline of the West Point slum on February 9, 2016 in Monrovia, Liberia. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 09: A teddy bear sits on a bed where a feverish baby Benson, 2 months, was taken to an Ebola treatment center in October 2014 in the West Point slum on February 9, 2016 in Monrovia, Liberia. Benson died two days later from Ebola. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
MONROVIA, LIBERIA - FEBRUARY 09: Cinema goers come to watch a movie in the West Point slum on February 9, 2016 in Monrovia, Liberia. West Point, the most impoverished and overpopulated community in Liberia, was hard hit by the Ebola outbreak. After almost two years, on January 14, 2016 the World Health Organization declared the epidemic over, after the virus had killed some 11,300 people and infected more than 28,500 people in West Africa. (Photo by John Moore/Getty Images)
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"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 WHO's Dr. Marie-Paule Kieny, who led the trial.

Related: Experimental Vaccine Could Stop Ebola

It's not a surprise - researchers had been working on an Ebola vaccine for years but because the virus only usually caused occasional, small outbreaks, it was hard to test it.

"VACCINE EFFICACY WAS 100 PERCENT."

Plus no governments or companies had invested the time or money needed to develop a vaccine.

Then the epidemic started in Guinea, Sierra Leone and Liberia in late 2013. By the time it was completely stopped earlier this year, it had infected 28,000 people and killed more than 11,000 of them.

Researchers rushed several vaccines into production.

This vaccine was developed by the Public Health Agency of Canada, which licensed it to a company called NewLink Genetics. Pharma giant Merck & Co. bought the license and is making it.

Related: Ebola Vaccine Trials Offer Hope

It uses an animal virus called vesicular stomatitis virus (VSV). The virus is harmless to people. Vaccine makers genetically engineered it to carry a little piece of Ebola DNA to stimulate an immune response.

Experts including Dr. Donald A. Henderson of John Hopkins University, who helped led the campaign to eradicate smallpox, designed a ring vaccination trial. Henderson died in August.

By the time all this work was done, the epidemic was waning. It's hard to test a vaccine if the disease is not spreading, but the international team tried it out in a coastal region of Guinea where Ebola cases were still being reported.

Related: Experimental Ebola Shot Looks Good

The virus spreads by direct contact, either between people or with bodily fluids such as blood from someone very ill with Ebola, or who has died from it.

The researchers tracked down every person who may have been in contact with a case, including family members and friends. Then they found people who had been in contact with those people. Each of these "rings" ended up including about 80 people.

Half got the vaccine and half did not.

The trial was stopped when it became clear that the vaccine was truly protecting people from infection, even after they'd been in direct contact with an Ebola victim.

The Food and Drug Administration gave the vaccine breakthrough designation to allow quick licensing.

GAVI, the Vaccine Alliance, has made a $5 million down payment to Merck to make sure the vaccine is available when it's next needed. Merck has promised to make 300,000 doses of the vaccine available for emergency use.

"Ebola left a devastating legacy in our country. We are proud that we have been able to contribute to developing a vaccine that will prevent other nations from enduring what we endured," said Dr KeÏta Sakoba, coordinator of the Ebola response in Guinea.

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