New Ebola Vaccine Shows 100 Percent Effectiveness In Early Tests

Could help prevent another deadly outbreak like the one in West Africa

Ebola virus infects a monkey cell.

NIAID/Flickr

At this time last summer, the horrific and often fatal disease Ebola was ravaging West Africa in the deadliest outbreak of its kind in recorded history, even causing undue panic around the world in areas at low risk, such as the United States. While the worst spread of the disease has been contained, the threat of a future Ebola outbreak persists. But in an extremely promising medical advance, scientists are now saying that an experimental Ebola vaccine with 100 percent effectiveness has been developed.

A paper published today in the British medical journal Lancet reports that the vaccine, which has been tested in Guinea since March 2015, has shown extraordinary results so far, with 4,123 people voluntarily vaccinated and all safe from the disease.

The joint study—conducted by international teams from the World Health Organization, the Guinean Health Ministry, Doctors Without Borders, the Norwegian Institute of Public Health and the nonprofit Epicentre research center, among many others—has been 100 percent effective in vaccinated individuals. "This is an extremely promising development," said Dr. Margaret Chan, the Director General of the World Health Organization (WHO), in a statement issued earlier today. However, she and the reviewers of the study are keen to point out that these are preliminary results, and advise the trial to continue.

“This is an extremely promising development."

The medical authorities carrying out the trial have been using what’s known as a “ring vaccination strategy” to test the vaccine’s efficacy. This involves inoculating all known contacts of an infected individual, thereby creating a ‘ring’ of inoculation around the disease and stunting its spread. This technique was used to tremendous success in the eradication of smallpox.

John-Arne Røttingen, Director of the Division of Infectious Disease Control at the Norwegian Institute of Public Health, also noted in the WHO's statement that it was this strategy in particular that has allowed for them to follow the dispersed epidemic in Guinea, which has dwindled significantly (The WHO reported seven cases in the affected region of West Africa last week—the lowest number of new patients in over a year) and to continue testing.

Furthermore, while VSV-EBOV has shown 100 percent efficacy in individuals, more conclusive evidence is necessary to prove the vaccine’s ability to protect larger populations from the disease, according to the WHO. This trait, known as “herd immunity,” is especially vital in order for the vaccine to be truly successful.

The trial faced some obstacles in the beginning, particularly for using no placebos, and for carrying out testing and research in the midst of an emergency.

Some have argued that the results could be skewed positively because volunteers knew they were receiving the actual vaccine. This raised a number of questions on ethical and scientific grounds, but were ultimately dismissed by the medical teams involved for practical reasons.

Jeremy Farrar, director of Wellcome Trust, a major supporter of the research, commented on this in an interview with the New York Times saying the fact that the trial still achieved positive results in spite of various constraints and limitations, actually vindicates the design and approach taken to the study.

"a turning point in the history of health research and development."

The latest Ebola outbreak in West Africa —centered largely on Sierra Leone, Liberia and Guinea— is the most widespread and deadliest in recorded history, having killed over 11,000 people in the span of less than two years. Although the outbreak is down significantly today, there have been a number of high risk instances in Sierra Leone and Guinea recently, with over 2,000 contacts still within their 21 day monitoring period, so the early success of VSV-EBOV could be instrumental in bringing this current outbreak down to zero.

This month, the WHO is expected to review the results of the study and make recommendations for future use. It is expected that this vaccine will likely be used to stop future outbreaks rather than vaccinate whole populations.

Regardless of the specifics of how it is to be used in the future, the significance of this trial on emergency health strategies going forward cannot be understated. The speed and efficiency with which this vaccine was developed and tested in the midst of a global medical emergency is unparalleled. As WHO's assistant director general Marie-Paule Kieny said in today's news release: "This record-breaking work marks a turning point in the history of health research and development."