When the trials began in Liberia on Monday February 2, 2015, about a dozen people received the vaccine, according to Wessedi Sio Njoh, Director of Operations with the Partnership for Ebola Vaccination. "Twelve persons for today and hopefully the number will increase as we go along," she said.

The hospital where the trials began is located at New Kru Town, a densely populated, poor shanty community. New Kru Town was one of the first parts of the capital to be struck by Ebola.

During this phase of the trials, Njoh told DW they intend to obtain "more information about the safety and efficacy" of the vaccines. In the next phase, they will target 27,000 people.

Scientific trials usually involve giving a certain group (the 'control' group) an inert substance while a second group receives the actual vaccine. But if there is potentially a high level of exposure to a lethal virus, as in the case of Ebola, such a procedure "poses an ethical question," according to DW science editor Fabian Schmidt.

It was vital that everyone in the control group taking part in the tests should be closely monitored and should immediately be given proper treatment should he or she become infected, Schmidt said.

Physician's assistant Emmanuel Lansana was one of the first volunteers. He told DW that counselling had cleared up his initial reservations.

"I was told about the side effects. We were told we should expect effects like headache, pain at the injection site, fever, and you may have joint pains," he said.

Assistant Health Minister Tolbert Nyenswah told DW the first phase of trials had gone well.

"The vaccine cannot give you Ebola," said Nyenswah. "There are some side effects like headache and vomiting. It is like any other drug with side effects. 400 people have taken this vaccine; some in the United States and others in Europe and Mali and we have not heard about any death among them."

Many Liberians unconvinced

In spite of such assurances, many Liberians remain skeptical. Rita Juah, 40, said when the epidemic began, the message had been that "Ebola does not have medicine or treatment."

"I will not allow my child or myself to take that vaccine," said Juah. "I will not allow anyone closer to me to take that vaccine."

Jemama Nailo, 42, said she would stay away from the vaccination center. Ebola had been a tragedy for her and her family. "It killed my loved ones, my blood sister, my oldest brother’s son, my brother's mother-in-law, and they left many children with me,” she said." “How will I know that the vaccine they brought is something that will help us from Ebola? I am just depending on Almighty God."

However, Ebola awareness campaigner Mercy Nyumah said she welcomed the trials. "When I heard the radio announcement about the vaccine, I said to myself I will be one of those to go for the trial," she told DW.

The vaccine trials come as significant falls in the number of deaths from Ebola are being recorded in the three most affected countries - Guinea, Liberia and Sierra Leone.