Children under 6 months old get a flu booster. how do you get reimbursed for the booster? I have billed 90688 with 90471 for the first shot 4 weeks later child comes back for the booster. According to the nurse she gives .5 ml the first time then second visit she administers the other .5. Some coders say to post 90688 with 90471 once and do not bill for the booster. I can see that if you are giving .25 then the other .25 when baby comes back in 4 weeks but how do you get reinburse for the second .5? and if nurse is giving the full .5 why do everyone calls it a HALF dose?