An experimental vaccine against the Ebola
virus, developed in Canada, in conjunction
with the World Health Organisation (WHO)
has been found to be 100% effective.
According to a report published in The
Lancet, a British medical journal on Thursday,
the vaccine called RVSV-ZEBOV offers hope of
better protection against the disease that
ravaged West Africa in 2014, killing more
than 11,000 people.
“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, the
director of the National Agency for Health
Security in Guinea.
The experimental vaccine was given in 2015
to people in Guinea who were in contact with
patients who had recently confirmed cases of
A few months after the early trials, the WHO
said the preliminary results were an “extremely promising development.” Initially, only people over the age of 18 were offered the vaccine and the participants receiving them were randomised.
But the process was stopped after initial
results in order to get the vaccine to
everyone in need of it.
The trial involved more than 11,000 people,
according to the WHO, that led the trial in
conjunction with Guinea’s Ministry of Health.
When analyzing the results, the teams didn’t
count people who got sick within the 10
days, as they were believed to have been
infected before they received the vaccine.
Waiting 10 days also gave volunteers time to
build up immunity after receiving the
vaccine, according to Dr. Marie-Paule Kieny,
WHO’s Assistant Director-General and the
study’s lead author.
Patients were either vaccinated immediately
or after three weeks. As everyone had become eligible for the vaccine, the three- week group served as the control as they didn’t actually get the vaccine until it was clear that they were not infected (Ebola has an incubation time of two to 21 days), Kieny said.
Researchers followed up with immunized volunteers at their homes on days three, 14,
21, 42, 63 and 84 after receiving the vaccine.
A total of 5,837 people were given the RVSV-
ZEBOV vaccine, and none had a recorded case of Ebola after 10 days or longer, the study says.
Among people who were not immediately
given the vaccine, there were 23 cases.
Some people who had the vaccine reported
headaches, fatigue and muscle pain. Two
patients had serious reactions, including one
who had an allergic reaction.
There are multiple strains of the Ebola virus,
and this vaccine covers the Zaire group and
offers cross-protection for similar strains in
this group, Kieny said.
“The principle is to stop transmission,” Kieny
said. “So you are one step quicker than the
transmission of the disease.”
To enable this, researchers doled out the
vaccine to so-called “clusters” or “rings” —
groups of people who had been in contact
with an Ebola patient.
It’s the same strategy that was used to
“The premise is that by vaccinating all people
who have come into contact with an infected
person, you create a protective ‘ring’ and
stop the virus from spreading further,” John-
Arne Rottingen of the Norwegian Institute of
Public Health, which has been involved in
implementing the trial, told CNN last year.
The vaccine was developed in Canada but is
now owned and manufactured by Merck,
Sharp & Dohme. It’s currently being fast-
tracked by US and European regulatory
A new vaccine takes about 10 years, on
average, to become available, according to
Merck has promised to ensure that 300,000
doses of the vaccine will be available in case
of a new Ebola flareup. It will submit the
vaccine for licensing by the close of 2017.
“When the next Ebola outbreak hits, we will
not be defenseless,” Kieny said.
Other vaccines are also being studied, Kieny
Ebola was first discovered in 1976, and
before the 2014 outbreak, it typically hit
isolated African communities — those
outbreaks were much more manageable for
medical teams to parachute in and treat
But the virus reached cities in 2014,
spreading like wildfire and catching the
global health community off guard.
Ebola is highly contagious once patients are
symptomatic, so as families and close-knit
communities tried to care for sick loved ones,
they risked infection themselves. A vaccine,
however, can protect them.