Federal officials said on Thursday that the first clinical trial to test the effectiveness of Ebola vaccines was expected to begin in Liberia in two weeks.
Volunteers in the trial will be given either a vaccine being developed by GlaxoSmithKline, a vaccine being developed by Merck or a placebo. There are expected to be 9,000 people in each arm of the trial.
GlaxoSmithKline, which is based in Britain, said on Friday that it was shipping the first few hundred doses of its vaccine to Liberia, using a commercial flight from Belgium, where its vaccine division is based.
“This has been an unprecedented effort for everyone involved,” Andrew Witty, Glaxo’s chief executive, said in an interview.
The number of new Ebola cases is waning in West Africa. Officials from the United States Department of Health and Human Services said that could make it harder to determine if either of the vaccines was preventing disease. More participants may have to be added to the trial, or it may need to be expanded to neighboring Sierra Leone, they said.
The officials also said a trial would start soon in Liberia to test ZMapp, a drug for patients already infected with the virus.