A prospective, randomized, double-blind phase 1 safety and immunogenicity study of the HD compared with the SD TIV in pediatric patients between the ages of three and 17 yr that have undergone SOT (Clin-Trials.gov. NCT01525004) was conducted. Subjects were randomized in a 2:1 fashion to receive 0.5 mL of either the HD (60 μg) or SD (15 μg) TIV intramuscularly. Subjects <9 yr of age received either one or two doses of the vaccine based on ACIP recommendations [19]. The study was approved by Institutional Review Boards at both institutions (Vanderbilt University, Nashville, TN, and the University of Pittsburgh, Pittsburgh, PA) and conducted during the 2011-2012 influenza season. Subjects were randomly allocated to either the HD or SD group by a computer-generated allocation system. Participants, their families, and research staff who performed clinical evaluations remained blinded to the child's assigned dosage, while designated unblinded nurses administered the requisite vaccine.