Two potential vaccines against the deadly Ebola virus ravaging West Africa could be available as soon as November and would first be given to health care workers most at risk of exposure to the disease there, the World Health Organization announced on Friday.

The organization also announced that blood from recovered Ebola patients and serums derived from that blood should be used to treat the sick, and it said treatment centers should quickly begin testing other experimental therapies to combat the viral disease, which has escalated into a devastating health crisis.

“We have to change the sense there is no hope in this situation to a realistic hope,” Dr. Marie-Paule Kieny, an assistant director general, told a telephone news conference at the conclusion of a two-day meeting at the organization’s Geneva headquarters aimed at expediting the prevention and cure of Ebola. The disease has now killed nearly 2,100 people over the past six months. Nearly all the deaths have been in three West African countries — Guinea, Liberia and Sierra Leone — but clusters of Ebola patients have recently been found in Nigeria, Africa’s most populous country.

Dr. Kieny said nearly 200 scientists, ethicists and clinicians from around the world had reached a consensus in identifying the most promising vaccines and potential treatments and developing strategies for testing them. The two vaccines, which have not yet been studied in humans, are set to undergo initial tests of their safety and immune system effects beginning this month in a small number of volunteers in Britain, the United States and Mali, which borders Guinea, where the outbreak emerged.