First identified by The Patterning:
I like to call this melodic snippet the “Millennial Whoop.” It’s a sequence of notes that alternates between the fifth and third notes of a major scale, typically starting on the fifth. The rhythm is usually straight 8th-notes, but it may start on the downbeat or on the upbeat in different songs. A singer usually belts these notes with an “Oh” phoneme, often in a “Wa-oh-wa-oh” pattern. And it is in so many pop songs it’s criminal.
And enjoy Quartz’s video compendium of Millenial Whoop examples: