The epidemic "has already affected 115,600 children and killed 1,145" between January and June, the UN Office for the Coordination of Humanitarian Affairs (OCHA) said in a statement.
This prompted the vaccination of 3.1 million children across five provinces it added.
The campaign swung into action in May after the NGO Medecins Sans Frontieres (MSF) deplored "the lack of reactivity" of organisations like the World Health Organisation to what it termed an "uncontrollable" epidemic.
The DR Congo is also battling cholera and polio epidemics. (*)