Comparison of Flu Vaccine Doses in Children

Influenza is an important cause of morbidity and mortality among both children and adults. Influenza A and/or B viruses cause yearly epidemics in the United States with an average of 36,000 deaths and 114,000 hospitalizations annually. Children have the highest rates of infection. Influenza is also associated with substantial numbers of hospitalizations among young infants. Because of the limited data available and the variability of reported seroresponses to doses of 0.25 ml in children 6-35 months of age, investigators hypothesize that a higher dose will be more consistently immunogenic. In addition, since currently licensed trivalent inactivated influenza (TIV) vaccines are well tolerated with minimal systemic and local adverse events, investigators hypothesize that administering a higher dose of 0.5 ml to this age group will be well-tolerated. Therefore, investigators propose to compare the safety and immunogenicity of 0.25 ml doses of TIV to that of 0.5 ml doses of TIV when administered to children 6-35 months of age. The proposed study is a phase I, two-arm, 1:2 randomized, double-blinded trial comparing the safety and immunogenicity of increased dose(s) (0.5 ml) with standard dose (0.25 ml) of TIV in children 6-35 months of age with and without a history of previous TIV vaccination. The population will include a Naïve Cohort: 270 healthy male and female children who are 6-35 months of age and have never received an influenza vaccination; and a Fully Primed Cohort: 60 healthy male and female children who are 12-35 months of age and have received two doses of 2009-2010 H1N1 and two doses of TIV at anytime in the past as defined for purposes of this study. Either a standard pediatric dose (0.25 ml) or a larger dose (0.5 ml) of TIV will be administered intramuscularly in the anterolateral thigh with a 25 gauge 1" needle. The primary objective is to evaluate the safety of administering an increased dose(s) (0.5 ml) of TIV to children 6-35 months of age as compared to standard dose(s) (0.25 ml) of TIV. The secondary objective is to compare the humoral immune responses to TIV antigens in children 6-35 months of age who receive the increased dose(s) of TIV to those who receive the standard dose(s) of TIV.