Final trial results confirm Ebola vaccine provides high protection: WHO
An experimental vaccine has been found to be highly protective against the deadly Ebola virus in a major human trial in Guinea, the World Health Organisation has said.
The vaccine is the first to prevent infection from one of the most lethal known pathogens and the findings add weight to early trial results published in August last year. (http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(15)61117-5/abstract).
The fatal disease has reportedly killed 11,315 people since the first death was reported in March, 2014 in six countries — Liberia, Guinea, Sierra Leone, Nigeria, the US and Mali. Close to 30,000 people were infected.
However, in January this year, the WHO declared the last of the countries affected, Liberia, to be Ebola-free.
The vaccine called rVSV-ZEBOV was studied in a trial involving 11,841 people in Guinea during 2015. Among the 5,837 people who received the vaccine, no Ebola cases were recorded 10 days or more after vaccination, according to results published in the medical journal The Lancet. In comparison, there were 23 cases 10 days or more after vaccination among those who did not receive the vaccine.
The trial was led by the WHO, together with Guinea’s ministry of health, Medecins sans Frontieres and the Norwegian Institute of Public Health, in collaboration with other international partners.
“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,” Dr Marie-Paule Kieny, WHO’s assistant director-general for health systems and innovation and one of the lead researchers in the trial, said.
The vaccine’s manufacturer, Merck, Sharpe & Dohme, this year received Breakthrough Therapy Designation from the United States Food and Drug Administration (USFDA) 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 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 it started in 2015.
Initially, only adults over 18 years were offered the vaccine but after interim results were published showing the vaccine’s efficacy, the trial was also opened to children older than 6 years.
“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,” Dr KeÏta Sakoba, coordinator of the Ebola Response and director of the National Agency for Health Security in Guinea, 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 a 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.
Additional studies are ongoing to provide more data on the safety of the vaccine in children and other vulnerable populations such as people with HIV.
The rapid development of rVSV-ZEBOV contributed to the development of WHO’s R&D Blueprint, a global strategy to fast-track the development of effective tests, vaccines and medicines during epidemics.