HELP!!! FLu Shot CPT® code

Should Q2038 be used for ALL insurances or is this code ONLY used on MEDICARE patients with G0008? Also, for a pediatric flu shot, should we use the code of 90471 with the Q code? Our peds usually have Medicaid as their carrier. Or should I be using 90657 or 90658?? Is this the correct way to code these visits? We just started giving flu shots and I need clarification before I get further into entering flu shots. I guess my general question would be: is the Q2038 used only on Medicare patients, NOT Medicaid???? Your quick response would be so greatly appreciated so until then, I will hold my flu shot visits for entry. Thank you!