- At risk for difficult-to-treat middle ear infection defined as having a minimum of 1 of the following: recurrent middle ear infection (defined as >=3 episodes, including the current episode, of rapid onset of rapid onset of severe middle ear infection during the 6 months before the study or >=4 episodes, including the current episode, of rapid onset of rapid onset of severe middle ear infection during the year before the study), persistent middle ear infection defined by signs and symptoms of rapid onset of severe middle ear infection on the third day after starting any antibiotic treatment (with the exception of amoxicillin/clavulanate that included >=90 milligrams/kilograms/day [mg/kg/day] of amoxicillin)