How Can A Brain Injury Be Treated?

My adult son was injured in an motor vehicle accident in April, suffered a TBI, and is taking Symmetrel as one of three stimulant meds. Two others have been discontinued. As his caregiver, I would like him to have the flu vaccine. I am aware that he cannot have the live intranasal version, but can he have the killed virus injectable? Or is that vaccine completely killed vs. weakened? We have recently moved to a new locale immediately following his discharge from his final rehab facility. Although we have engaged a new PCP, our first appt. isn t til Nov. and i was instructed to use an urgent care facility if needed in the interim. My son has a Pm & R, but he doesn t have an answer for me. Thank you