The women, ages 39 and 27, are the first people to receive the vaccine, which had previously been tested only in monkeys, ABC News reported.
The fast-tracked clinical trial will test the safety of the vaccine and will include 20 men and women ages 18 to 50. No one will be infected with the disease. The vaccine was developed by the U.S. National Institute of Allergy and Infectious Diseases (NIAID) and drug maker GlaxoSmithKline.
Human testing of the vaccine was expedited due to West Africa's Ebola outbreak that has killed more than 1,900 people.
"There is an urgent need for a protective Ebola vaccine, and it is important to establish that a vaccine is safe and spurs the immune system to react in a way necessary to protect against infection," NIAID Director Dr. Anthony Fauci said in a statement.
In a related matter, drug maker Johnson & Johnson said Thursday that it will seek to "fast-track" the development of what is called a promising new combination vaccine against Ebola. The start of the trial is scheduled for early 2015.
U.S. and global health officials on Wednesday underscored the need for greater resources -- both medical and financial -- to fight the Ebola outbreak in West Africa. The spread of the disease is outpacing efforts to control it, it could pose a global threat and will cost at least $600 million to contain it, officials said.
"This is not an African disease. This is a virus that is a threat to all humanity," Gayle Smith, special assistant to President Barack Obama and senior director at the U.S. National Security Council, told reporters during a news briefing, the Associated Press reported.
The highly virulent disease is spreading faster than health workers in Guinea, Liberia, Nigeria and Sierra Leone can manage, Dr. Tom Kenyon, director of the U.S. Centers for Disease Control and Prevention's Center for Global Health, said during the briefing.
The World Health Organization has predicted that as many as 20,000 people in West Africa could become infected within three months.
Kenyon, who recently visited West Africa, said the tools to stop the outbreak exist -- they just have to be put in place. He said more treatment centers are being opened and talks are under way with the African Union to send additional health workers to the continent, the AP reported.
"I think we're confident if we put these treatment units up, the health workers will come, but of course they have to be adequately trained and supervised and equipped with personal protective equipment," he said.
The big challenge right now is that the affected countries don't have the resources they need. Hospitals don't have enough beds, and there aren't enough ambulances, Keiji Fukuda, the World Health Organization's assistant director-general for health security, said at a separate news briefing, USA Today reported.
Fukuda said basic needs aren't being met in the hardest hit countries, the newspaper reported. "Bodies are not being taken away quickly enough," he said. "People are hungry in these communities. They don't know how they are going to get food."
Dr. Tom Frieden, director of the CDC, said Ebola is primarily being spread in West Africa in two ways. The first way, among people caring for people with the disease, whether at home or in health-care settings and hospitals. The second way: unsafe burial practices.
Frieden said that since March the U.S. government has committed $20 million to combat the outbreak. In addition, the World Health Organization has asked for nations to commit $450 million to the fight, he said.
Meanwhile, the third American health care worker infected with Ebola is being cared for at a hospital in Liberia run by the medical missionary group he belonged to.
Dr. Richard Sacra is a 51-year-old family doctor who trained and worked in Worcester, Mass., but spent most of the past 20 years in Liberia. He was not treating Ebola patients but working in an obstetrics ward at a hospital in Liberia when he became ill, the Boston Globe reported.
It's not clear when Sacra might return to the United States for treatment.
Two other American health care professionals, Dr. Kent Brantly, 33, and Nancy Writebol, 59, became infected with the Ebola virus while doing missionary medical work in Liberia. Both were flown back to the United States last month for aggressive treatment at Emory University Hospital in Atlanta and are no longer contagious.
For more on Ebola, visit the U.S. Centers for Disease Control and Prevention.