After a rapid response by health agencies and the rollout of a new vaccine, an Ebola outbreak in the Democratic Republic of Congo has been declared “largely contained” by the World Health Organization.

The outbreak was the first in which health authorities deployed a Merck vaccine field-tested in the waning days of the huge 2014 epidemic in West Africa.

More than 3,200 people were vaccinated in Congo; they included front-line health care workers, as well as family members and friends who had been in contact with known Ebola victims.

None of those vaccinated became ill, the Congolese health ministry said.

As of Tuesday, 53 cases that were laboratory-confirmed or considered “probable” had been detected, and 29 patients had died, according to the ministry. Although suspected cases continue to be reported, none have been confirmed by a laboratory since June 6.