Defeat infected is an objective in the Story Mission, The Dawn of New Pandora in Borderlands 2: Commander Lilith and the Fight For Sanctuary
- Having pushed the button, will reveal a Infected Badass Bruiser and beyond that an Infected Pod.
- Go through the newly raised gate to find yourself in Vaughn's HQ.
- Once in there, just wait for Vaughn to come over.
- Wait for him to get into position to complete the mission.