By Kemo Cham
An Ebola vaccine candidate which was tried in Guinea, Liberia and Sierra Leone has been found to provide 100 percent protection, raising hopes for a potential prevention of the deadly hemorrhagic fever disease, the World Health Organisation (WHO) announced Friday.
The experimental vaccine called rVSV ZEBOV was found to be effective against the virus in a trial in Guinea, details of the study published on the medical journal, the Lancet, earlier in the week show.
The breakthrough comes nearly a year after the end of the world’s deadliest Ebola outbreak that wreaked havoc in West Africa between 2014 and 2016. Over 11,300 people died, out of more than 28,000 cases globally, according to figures from WHO.
Sierra Leone, Liberia and Guinea, where it all started, bore the brunt of the cases and fatalities.
About half a dozen candidate vaccines were put on trial in response to the epidemic. rVSV EBOV, which is a Canadian made vaccine, was considered as one of the most promising experimental vaccines among the lot.
This is a vector vaccine, meaning that a small piece of Ebola virus that cannot cause Ebola is inserted into a different virus that’s harmless.
A team of three dozen researchers, headed by Marie-Paule Kieny, WHO's assistant director-general, found a 90-percent likelihood during a full-fledged epidemic that the vaccine would work in more than 80 percent of cases.
Initially developed by the Canadian Public Health Agency, rVSV ZEBOV was later acquired by the US pharmaceutical giant Merck which now holds its license.
The Guinea trial was the only one that involved the participation of Ebola cases, meaning it’s the only one designed to demonstrate the effect of the vaccine on Ebola.
WHO funded and led the trial in collaboration with the Ministry of Health there. Some 11, 000 people were involved in the trial. The vaccine was given to people who had come in contact with confirmed Ebola patients.
Of the 5,837 people given the rVSV-ZEBOV vaccine, none had a recorded case of Ebola after 10 days or longer, the study reveals.
From among another set of people who were not immediately given the vaccine, called the control group, 23 cases of Ebola were recorded.
This is described as the ‘ring strategy’. The idea is that by vaccinating all people who have come into contact with an infected person, a protective 'ring' is created so that the virus is stopped from spreading further.
This, experts say, was crucial because the West African epidemic was the first ever experienced in an urban setting.
A Guinean health official hailed the development.
"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," said Dr. KeÏta Sakoba, Director of National Agency for health security in Guinea.
As expected, however, there were some reports of side effects among those who took the vaccine. While some reported headaches, fatigue and muscle pain, two patients reportedly had serious reactions, including one who had an allergic reaction. But they all soon recovered, according to the authors of the study.
This breakthrough also comes after 40 years since Ebola was first discovered.
The virus was first identified in 1976 in the former Zaire, now the Democratic Republic of Congo. Since then there had been sporadic outbreaks with little fatalities, until the 2014 West African epidemic.
The UK firm Glaxosmithkline and the US-based Johnson & Johnson each has a candidate vaccine on trial for Ebola, as are China and Russia.
A standard approval process for a new drug or vaccine usually takes at least a decade.
Officials of the pharmaceutical firm behind the rVSV EBOV say it is expected to be available for use in 2018 as they intend put it through the fast-track approval process planned to be initiated next year.
But a few questions still remain unanswered about the vaccine.
These are its safety on children six and under, pregnant women, or people with the AIDS virus — all groups that were excluded from the most recent trials.
Another unknown is how long the vaccine’s effect lasts. The present findings only show that it provides protection very early after vaccination, and the effect only last after six months.
Hopefully, answers to these may be obtained from the trials in Sierra Leone and Liberia.
An official involved with the Sierra Leone trial told Politico recently that a key result that is pending and which was expected to be available early next year could provide answers for immune response to the vaccine and the duration of the protection that might be given by it.
Conducted under the Sierra Leone Trial to Introduce Vaccine against Ebola [STRIVE], the Sierra Leone trial was funded by the United States government through its Centers for Diseases Control (CDC) which also provided technical assistance to the College of Medicine and Allied Health Sciences of the University of Sierra Leone as lead researchers.
More than 8, 000 volunteers were vaccinated.
In Liberia the vaccine was trialed under the Partnership for Research in Ebola Virus in Liberia [PREVAIL], also a joint US-Liberia initiative.
All of the studies used slightly different scientific approaches but all were attempting to show an effect on the disease and to gather information on safety, Dr Barbara Mahon, the CDC’s Lead in STRIVE, told Politico in an earlier interview.
"The different studies ultimately will provide different information on the vaccine that can be used to support the application for licensing,” she said.
(C) Politico 26/12/16