Last week, as many of you were putting the finishing touches on your Christmas shopping and other holiday activities, the World Health Organization (WHO) announced that an experimental vaccine was found to be highly protective against the deadly Ebola virus in a major trial in Guinea, according to results published in The Lancet. [Ref 1] This news came as an early Christmas present for some researchers and health administrators on several continents and the global population.
The Ebola virus is spread by direct contact between people, as well as from contact with an infected person’s bodily fluids. The CDC tells us that the virus was first recognized during an outbreak in Zaire (Democratic Republic of the Congo – DRC) in 1976. The disease was transmitted to 318 persons (human cases) of which 280 died from this group. More recently, the Ebola outbreak began in Guinea in 2013, quickly spreading to both Liberia and Sierra Leone. The Ebola virus later spread to other countries including the United States and the United Kingdom.
How is the Ebola virus transmitted? Recall from an earlier post on the topic, NUMBERS: Ebola Virus Disease (EVD), researchers at WHO and other organizations have traced the origins of the disease to the fruit bats of the Pteropodidae family. The bats are considered to be natural Ebola virus hosts. Ebola is introduced into the human population through close contact with the blood, secretions, organs or other bodily fluids of infected animals such as chimpanzees, gorillas, fruit bats, monkeys, forest antelope and porcupines found ill or dead or in the rainforest.
Ebola then spreads through human-to-human transmission via direct contact (through broken skin or mucous membranes) with the blood, secretions, organs or other bodily fluids of infected people, and with surfaces and materials (e.g. bedding, clothing) contaminated with these fluids. Health-care workers have frequently been infected while treating patients with suspected or confirmed EVD. This has occurred through close contact with patients when infection control precautions are not strictly practiced.
This 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 last year. 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. In a comparison study, there were 23 cases 10 days or more after vaccination among those who did not receive the vaccine.
According to WHO, the vaccine’s manufacturer, Merck, Sharpe & Dohme, received Breakthrough Therapy Designation from the United States Food and Drug Administration and PRIME status from the European Medicines Agency this year! Both will enable faster regulatory review of the vaccine once it is submitted.
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.
“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 Dr Marie-Paule Kieny, WHO’s Assistant Director-General for Health Systems and Innovation, and the study’s lead author.
The CDC reports that between 2014 and 2016 more than 11,350 persons have died from the disease in several countries in West Africa and the Democratic Republic of the Congo where known outbreaks have occurred.
The effectiveness of the rVSV-ZEBOV vaccine in combatting the Ebola virus puts world health workers and those populations at greatest risk of contracting the virus in an excellent position for 2017.
- Final trial results confirm Ebola vaccine provides high protection against disease, in a News Release of the World Health Organization (WHO), December 23, 2016, http://www.who.int/mediacentre/news/releases/2016/ebola-vaccine-results/en/