"Since the outbreak began, the government of Uganda, together with researchers, funders, companies, regulatory authorities and other experts has been working under a global effort coordinated by WHO to accelerate the development and deployment of vaccines for use in trials," UN health agency chief Tedros Adhanom Ghebreyesus told reporters.
Speaking from the G20 summit in Indonesia, he said a WHO committee of external experts had evaluated candidate vaccines and determined "all three should be included in the planned trial in Uganda".
The WHO and Ugandan health ministry accepted the committee's recommendation, he said, adding, "We expect the first doses of vaccine to be shipped to Uganda next week."
The candidates include a vaccine developed by Oxford University and the Jenner Institute in Britain, and another from the Sabin Vaccine Institute in the United States.
The third candidate came through the International AIDS Vaccine Initiative (IAVI), WHO said.
In addition, Tedros said, a separate group of experts had selected two investigational therapeutics for a trial, which still requires a green light from WHO and Ugandan authorities.
Even without vaccines and therapeutics, Tedros stressed Kampala's efforts had "slowed transmission in most districts and two districts have not reported any cases for 42 days, indicating the virus is no longer present in those districts".
But he warned that Jinja had also reported its first case in the past week, "becoming the ninth district to be affected."
Since Uganda declared an Ebola outbreak on September 20, cases have spread across the country, including to the capital Kampala, and have claimed 55 lives, with 22 more believed to have died.
Uganda has been struggling to rein in the outbreak caused by the Sudan strain of the virus, for which there is currently no vaccine.
Ebola is spread through bodily fluids, with common symptoms including fever, vomiting, bleeding and diarrhea.
Outbreaks are difficult to contain, especially in urban environments.