WHO: Tests show new Ebola vaccine is 'highly effective'

By Doug Stanglin and Liz Szabo | USA TODAY

Show Caption Hide Caption We're getting closer to stopping Ebola Trials of a new Ebola vaccine have been successful in preventing the disease. Video provided by Newsy

Results of early tests of a new vaccine for Ebola shows it to be "highly effective," quickly protecting 100% of people against the virus, the World Health Organization said Friday.

"This is a landmark study," said Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, who wasn't involved in the trial.

The vaccine took effect within 10 days of vaccination, according to the study, published in The Lancet. that could make the vaccine very useful in an outbreak, Osterholm said.

"This is an extremely promising development," said Margaret Chan, Director-General of the WHO. "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."

Since late 2013, when the latest epidemic began in West Africa, there have been 27,600 Ebola cases, including more than 11,000 deaths. Liberia has suffered the worst, with more than 4,800 deaths, although the epidemic there has been better contained than in Sierra Leone and Guinea.

While doctors cheered the decline of the epidemic, they also worried that the falling number of cases would make it impossible to tell if vaccines were actually working, Osterholm said. He praised everyone involved in the current study for persevering under difficult circumstances.

An effective vaccine could help control Ebola outbreaks, by preventing sick people from infecting those around them, as well as protecting doctors, nurses, hospital staff and burial teams, who are at high risk, Draguez said.

Doctors hope the Ebola vaccine will protect even more people through a phenomenon called "herd immunity," in which vaccination decreases the amount of virus in circulation, protecting people who haven't had the shot.

"Too many people have been dying from this extremely deadly disease, and it has been very frustrating for healthcare workers to feel so powerless against it," said Bertrand Draguez, medical director for Doctors Without Borders. "More data is needed to tell us how efficacious this preventive tool actually is, but this is a unique breakthrough."

While the study results are promising, some scientists describe them as bittersweet.

Scientists published early results for a different type of Ebola vaccine, using a type of virus called an adenovirus, in 2003, said Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine in Houston.

In 2005, researchers Heinz Feldman and Thomas Geisbert showed that another type of experimental Ebola vaccine, which used a virus called the VSV virus, protected monkeys extremely well against Ebola. That vaccine is the same one used in the current study in Guinea.

Geisbert said he has a "great feeling of pride" for his role in developing the vaccine, and that "it sure looks like it is doing some good."

Pharmaceutical companies had no interest in conducting human tests, however, because there wasn't a market for them. Unlike flu outbreaks, which are large and occur every year, Ebola outbreaks occur sporadically and unpredictably. Until the current epidemic in West Africa, Ebola outbreaks were usually small, with only a few dozen patients. Pharmaceutical companies only agreed to develop Ebola vaccines after the West African epidemic spiraled out of control last year, affecting thousands of people.

"It's sad to think how many lives could have been saved had the technology been available a few months earlier," Hotez said. "'Too little too late," as they say."

Scientists have encountered the same problem developing a vaccine against MERS, or Middle East Respiratory Syndrome. Although early results have been promising, no pharmaceutical companies are interested, said Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, in an interview this week.

"This is a wake-up call to the world," Osterholm said, saying the world needs to find way to develop vaccines against rare but devastating diseases. "These diseases may not be occuring with high frequency, but when they do occur, it can cause a major crisis."

Doctors must now decide on the most effective use of the Ebola vaccine.

Draguez suggested focusing on a target group of people at highest risk for Ebola would be more effecting than mass vaccinations, noting that the outbreak of the diseased is in localized communities, rather than nationwide in any country.

"The 'ring' vaccination method adopted for the vaccine trial is based on the smallpox eradication strategy," said John-Arne Røttingen, Director of the Division of Infectious Disease Control at the Norwegian Institute of Public Health and Chair of the Study Steering Group. "The premise is that by vaccinating all people who have come into contact with an infected person you create a protective 'ring' and stop the virus from spreading further. This strategy has helped us to follow the dispersed epidemic in Guinea, and will provide a way to continue this as a public health intervention in trial mode."

The Guinea vaccination trial began in affected communities in March to evaluate the efficacy, effectiveness and safety of a single dose of the vaccine VSV-EBOV by using a ring vaccination strategy. So far, more than 4 000 close contacts of almost 100 Ebola patients, including family members, neighbours, and co-workers, have voluntarily participated in the trial.

There are still important questions about the vaccine, Hotez said. For example: Will the vaccine remain "stable" even when transported throughout Africa using coolers? How much vaccine should countries or health agencies stockpile?

"The hope, of course, is that this is a vaccine that will never have to be used, but one thing we learned about the 2014 epidemic is how little we still know about Ebola virus infection," Hotez said.

uMohamed Soumah, 27, was the first person to receive the Ebola vaccine. "It wasn't easy. People in the village said that the injection was to kill me," he said, according to a report by WHO. "I was afraid. I was the first one to be injected, the very first, here in my village (in March). I've been monitored for 3 months and I've had no problems. The last follow-up, 84 days after the vaccination, was all clear."

The authors of the interim review in The Lancet said they believe the results of the trials "are also likely to be externally valid and

applicable to other regions of Guinea and to Sierra Leone and Liberia, the other two countries in west Africa most severely affected by the ongoing epidemic."

The trial stopped randomization in late July to allow for all people at risk to receive the vaccine immediately, and to minimize the time necessary to gather more conclusive evidence needed for eventual licensure of the product, WHO said. Until now, 50% of the rings were vaccinated 3 weeks after the identification of an infected patient to provide a term of comparison with rings that were vaccinated immediately. This will now be ended. In addition, the trial will now include 13 to 17-year-old and possibly 6 to 12-year-old children on the basis of new evidence of the vaccine's safety.

The vaccine, known as VSV-EBOV, was developed by the Public Health Agency of Canada.