LONDON/GENEVA (Reuters) - Final stage trials of an Ebola vaccine being developed by Merck and NewLink Genetics will begin in Guinea on March 7, the World Health Organization said on Thursday.
Signaling global health authorities’ determination to see through trials despite a sharp drop in cases in the West Africa epidemic, the WHO said a second shot, developed by GlaxoSmithKline will be tested “in a sequential study, as supply becomes available”.
More than 23,900 confirmed and suspected cases of Ebola have been reported since the outbreak began in December 2013, including some 9,800 deaths. Nearly 500 health workers have been among the dead in what is the worst ever Ebola epidemic.
All three worst-hit countries - Guinea, Liberia and Sierra Leone - aim to conduct final-stage trials of vaccines, and Liberia is already testing the GlaxoSmithKline and Merck-NewLink shots, while Sierra Leone is expected to announce plans soon.
But recent steep declines in new Ebola cases will make it far harder to prove whether experimental vaccines work, as the vaccine’s effect will be difficult to establish.
The WHO, however, said it was committed to pushing ahead.
“The Ebola epidemic shows signs of receding but we cannot let down our guard until we reach zero cases,” said Marie-Paule Kieny, head of the WHO’s Ebola research and development effort.
“An effective vaccine to control current flare-ups could be the game-changer to finally end this epidemic and an insurance policy for any future ones.”
The trial in the Basse Guinée region, which has Guinea’s most cases, will use a “ring vaccination” strategy similar to that used to eradicate smallpox in the 1970s. This involves vaccinating everyone who has been in contact with a newly diagnosed person or “index” case.
“Testing investigational medicines during an epidemic is incredibly challenging, but this approach gives us the best possible chance of finding a safe and effective vaccine in time to save lives,” said Jeremy Farrar, director of Wellcome Trust, the medical charity that has led the push for Ebola vaccines.
In Liberia, where no new cases have been reported for 13 days, the government says the trial is a “resounding success”.
But local media has reported that some residents are refusing measles and polio vaccinations amid rumors of a deliberate plot to infect them with Ebola.
Additional reporting by James Harding Giahyue in Monrovia and Emma Farge in Dakar; Editing by Louise Ireland