An estimated 20,000 children are hospitalized each year with influenza-related illnesses. Children with certain chronic conditions are at higher risk for serious influenza (flu) complications, and recommendations for annual flu vaccines have been targeted at these children. Over the past four years, public health officials have expanded their recommendations about which children should be immunized against the flu. This Issue Brief summarizes clinical outcomes and costs from the largest study to date of children hospitalized with the flu. These findings should help inform clinicians and policymakers in prioritizing their efforts to implement the new recommendations.