The World Health Organisation has endorsed the final results of the clinical trial of an Ebola prototype vaccine.
The global body in a statement in Geneva, Switzerland on Wednesday noted that the final trial results confirmed that the Ebola vaccine provided high protection against the disease.
The vaccine called rvsv-ZEBOV, according to results published in The Lancet , was studied in a trial involving 11,841 people in Guinea in 2015.
WHO’s Assistant Director-General for Health Systems and Innovation, and the study’s lead author, Dr Marie-Paule Kieny, stated that among the 5,837 people who received the vaccine, no Ebola cases were recorded 10 days or more after vaccination, while there were 23 cases about 10 days among those who did not receive the vaccine.
The trial was led by WHO, together with Guinea’s Ministry of Health, Medecins sans Frontieres and the Norwegian Institute of Public Health, in collaboration with other international partners.
Kieny said, “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 defenceless.”
The vaccine’s manufacturer, Merck, Sharpe & Dohme, this year received Breakthrough Therapy Designation from the United States Food and Drug Administration and PRIME status from the European Medicines Agency, enabling faster regulatory review of the vaccine once it is submitted.
Since Ebola virus was first identified in 1976, sporadic outbreaks have been reported in Africa. But the 2013–2016 West African Ebola outbreak, which resulted in more than 11, 300 deaths, highlighted the need for a vaccine.
The trial took place in the coastal region of Basse-Guinée, the area of Guinea still experiencing new Ebola cases when the trial started in 2015. The trial used an innovative design, a so-called “ring vaccination” approach — the same method used to eradicate small pox.
When a new Ebola case was diagnosed, the research team traced all people who may have been in contact with that case within the previous three weeks, such as people who lived in the same household, were visited by the patient, or were in close contact with the patient, their clothes or linen, as well as certain “contacts of contacts”. A total of 117 clusters (or “rings”) were identified, each made up of an average of 80 people.
Initially, rings were randomised to receive the vaccine either immediately or after a three-week delay, and only adults over 18 years were offered the vaccine. After interim results were published showing the vaccine’s efficacy, all rings were offered the vaccine immediately and the trial was also opened to children older than six years.
In addition to showing high efficacy among those vaccinated, the trial also shows that unvaccinated people in the rings were indirectly protected from Ebola virus through the ring vaccination approach (so called “herd immunity”).
However, the Coordinator, Ebola Response and Director of the National Agency for Health Security in Guinea, Dr. Keïta Sakoba, noted that the trial was not designed to measure this effect, so more research will be needed.
“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,” Sakoba said.
To assess safety, people who received the vaccine were observed for 30 minutes after vaccination, and at repeated home visits up to 12 weeks later. Approximately half reported mild symptoms soon after vaccination, including headache, fatigue and muscle pain but recovered within days without long-term effects. Two serious adverse events were judged to be related to vaccination (a febrile reaction and one anaphylaxis) and one was judged to be possibly related (influenza-like illness). All three recovered without any long term effects.
