We are now almost a year and a
half into a severe epidemic in West Africa caused by Ebola virus with a total
of 27,748 cases and 11,294 deaths (41%) until July 26 2015.

Celebrations in Liberia after becoming Ebola free in May 2015. A couple
of new cases resurfaced 7 weeks later.

This outbreak could have been
prevented if a vaccine had been available. But since 1976, the year of the
first outbreak of Ebola virus in the Democratic Republic of Congo, no vaccine
has been developed, although there were no scientific and technical barriers.
There are two main reasons for that. 1. Until 2013 there were several new
outbreaks, due to contact with monkeys and fruit bats carrying the virus, but
they were always contained because communities understood that the disease is
transmissible and can be controlled by hygiene and isolation. In total 2387 cases
and 1590 deaths (67%) were recorded between 1976 and 2013

. 2. During these 37 years attempts were made to
develop a vaccine and many prototype vaccines were developed using seven
different vaccine platforms. Eight vaccines were even tested in primates, the
best model for man

. But further development was not undertaken, mainly
because of the high costs (several 100 millions of €) to develop a licensed
vaccine. For the pharmaceutical industry this would have been a project without
return on investment and there were no public or other parties feeling the need
to act. But after more than 2000 fatalities and the chance of an explosive

something had to be done. The WHO convened an
urgent meeting in which the two most promising vaccine candidates were selected
for further development. Both vaccines already showed promising results in
monkeys, the best model for man. Both vaccines are based on the Ebola virus
glycoprotein G but have different expression systems

. Phase 1 clinical trials were carried out and
showed that the two vaccines are safe for humans, meaning that phase 2/3
studies to measure the efficacy of the vaccines could start.

Today the results for one of
the two vaccines, developed by the Public Health Agency of Canada and produced
by Merck became available. The vaccine appears to be highly effective. The
Guardian reports

. Full scientific details as described in The Lancet can be found as a link in
this article.