One of the youngest survivors of the federal building bombing is back in the hospital.

Brandon Denny, who spent 98 days in hospitals and rehabilitation centers, is being treated for an infection in the left side of his head, where the April 19 blast smashed a hole in his skull.

Brandon, who turns 4 on Monday, was listed in fair condition in the intensive care unit at Presbyterian Hospital, where he was taken after his parents noticed a swelling on Thursday.

Brandon’s injury left him partially paralyzed and unable to speak. He underwent four brain operations after the federal building blast that killed 169 people and injured 500 more.