"One (piece of) good news is that this outbreak is under control now. We haven't had any new cases in Angola since June 23, and since July 12 in DRC (Democratic Republic of Congo)," Briand told a regular U.N. briefing in Geneva.

The entire Congolese capital of Kinshasa, 7.7 million people, had been vaccinated in less than 10 days, as well as 3 million in border areas to prevent transmission from Angola, and another 3 million on the Angolan side of the border, where a second phase of vaccinations would be carried out soon.

"So far in Angola more than 15 million people (have been vaccinated), this represents 65 percent of the population. So we still have to protect certain districts and provinces but the risk of a major outbreak I think is now over," she said.

But there were still 32 endemic countries in Africa, so further outbreaks could not be ruled out, including in the parts of Congo that had not been vaccinated recently, she said.

At the end of August the WHO said the trend was "extremely positive" but it was too early to say the outbreak had been stopped completely, with 1,000 confirmed cases and up to 6,000 suspected cases of the mosquito-borne disease.

The outbreak is the worst in decades among unprotected African populations and has killed more than 400 people.

The vaccination campaigns have depleted the global stockpile of 6 million doses twice this year, forcing doctors to switch to administering one-fifth of the normal dose, a tactic that the WHO says gives at least temporary protection from the disease.

On Monday experts from WHO and other health agencies met in Geneva to discuss a long-term strategy to prevent future large outbreaks of yellow fever.

The risk of such outbreaks has risen due to urbanization and increasing mobility of the population, and this year it was especially acute because of the El Nino weather phenomenon which multiplied mosquito numbers, she said.

The recent mass vaccination campaign aimed not only to stop the transmission of the virus but also to preempt transmission during the rainy season, which is already starting in some areas, Briand said.

(Reporting by Tom Miles; editing by Ralph Boulton; Editing by Dominic Evans)