Outpatient burden of laboratory-confirmed influenza among children in Knox and Davidson Counties was compared in 2006-2007 when only Knox County had a school-based influenza vaccine campaign. Of 1016 eligible children seeking outpatient care, 87% were enrolled and 20% were influenza-positive. Estimated influenza vaccination coverage was similar in Knox and Davidson for preschool-age children (36% versus 33%) but higher in Knox County for school-age children (44% versus 12%). Influenza detection was higher among Knox than Davidson County preschool-age children (18% versus 10%) but similar among school-age children (28% versus 27%). These data are consistent with a direct effect of the campaign in school-age children.