The World Health Organization said an experimental Ebola vaccine could be in use by January.
WHO assistant director Dr. Marie Paule Kieny said Tuesday that clinical trials of Ebola vaccines were underway or planned in Europe, the United States and Africa.
Kieny said said if the vaccines were deemed safe, there could be a West African trial in January, using tens of thousands of doses.
Speaking to reporters in Geneva, Kieny did not say when an Ebola vaccine might be widely available.
Airline passengers
Also Tuesday, the U.S. Homeland Security Department said it will require all passengers arriving in the United States from Liberia, Guinea or Sierra Leone to fly into one of five airports equipped with enhanced screening for the deadly disease.
JFK airport in New York became the first to begin the stepped-up screening on October 11. The other four airports - Newark in New Jersey, Dulles outside Washington, Hartsfield in Atlanta and O'Hare in Chicago - began the new protocols last week.
Homeland Security Chief Jeh Johnson said officials are "continually evaluating whether additional restrictions or added screening and precautionary measures are necessary to protect the American people."
The screening measures include taking the passengers' temperatures before admitting them into the United States.
The five airports accounted for about 94 percent of travelers flying to the United States from the three West African nations where the Ebola outbreak has hit hardest.
Spanish nurse's aide
Meanwhile, in Spain, health officials said two rounds of tests have shown that a nurse's aide who was infected with Ebola is now virus-free. Teresa Romero Ramos has been hospitalized since she tested positive for Ebola earlier this month.
On Monday, the WHO declared the nation of Nigeria free from Ebola after 42 days passed with no new reported cases.
But Nigerian President Goodluck Jonathan has directed all anti-Ebola measures in Nigeria to remain in effect, including health screenings for people entering the country.
Ebola Cases and Deaths in West Africa as of October 14, 2014.
Nigeria had 20 cases of Ebola and eight deaths as part of the worst-ever outbreak of Ebola.
In the United States, the Centers for Disease Control and Prevention (CDC) announced tighter guidelines for health care workers taking care of Ebola patients.
CDC officials issued the new procedures late Monday, saying that a health workers' protective clothes must leave no part of the body exposed and that a trained monitor must supervise workers as they put on and take off the clothing.
Quarantine lifted in Texas
In the southwestern U.S. city of Dallas, officials announced Monday that the 21-day quarantine has been lifted on 43 people who had contact with the state's first Ebola patient.
But Dallas Mayor Mike Rawlings said 120 others who had contact with one of the other Ebola patients were still being watched for signs of the virus.
Also in the United States, health workers at a special Ebola treatment unit said another patient has recovered from the virus. The man, who was not identified, was infected with Ebola while in Sierra Leone and was airlifted to the eastern U.S. city of Atlanta.
Separately, a United Nations spokesman said a staff member from U.N. Women in Sierra Leone died of Ebola in recent days, the third reported death of a U.N. worker from Ebola.
Liberia, Guinea, and Sierra Leone have been the hardest hit by the Ebola outbreak, with more than 9,100 cases.
The disease has killed more than 4,500 people in West Africa this year.
Some information for this report was provided by AP.